2 locations, 1 unit (any unit)
Whenever a unit goes to location X, and then to location Y, then a message should be displayed. This message should ONLY be displayed if that unit went to location X first, and then to location Y. The important thing is, that it has to be the same unit that went from location X to location Y, and not some other unit. So if there is 1 unit at location X, and another unit at location Y, no message should be displayed.
None.
If a player brings the exact unit required to location 'X', then set switch 1 (or whatever switch you want). If that same player brings the exact unit required to location 'Y', and switch 1 is set, then display the text message.
None.
Well, that will work, but to make certain, can we get a bit more info, my main question is, is there only 1 of the unit moving to the locations?
None.

We can't explain the universe, just describe it; and we don't know whether our theories are true, we just know they're not wrong. >Harald Lesch
Uh oh... that could get a little tricky.
Basically when you want to follow a certain unit always center a 1x1 pixel location on it.
The idea is when the unit enters x center the 1x1 pixel on it and set a dc (better than a switch) for that player to 1.
When he brings a unit to y create a burrowed unit at 1x1.
Then check if that unit is in y.
If yes, display the text and reset the dc.
The problem is you'll have to think about failsafes. E.g. When the player brings a unit to x then leaves x and brings another unit to x and this new unit to y then the new unit has no 1x1 location following, so the detect fails.
Depending on how many units can run around you could copy this system 10 times or so and always use another 1x1 location and another dc.
There may be more issues. Just try what I said and post any problems. We'll eventually get it working bugfree.
Yeah, in that case, it better not be an air unit..
None.
It is important to know what units do you have in your map roaming around. Are they all different types of units? Is there flying units? and etc.
Some.

We can't explain the universe, just describe it; and we don't know whether our theories are true, we just know they're not wrong. >Harald Lesch
Another idea: Now that ScmDraft supports unit IDs directly you could directly check for the unit ID instead of following it with a 1x1 pixel location. That would work for burrowing and flying units too.
But when you're not willing to make hundrets of copies of triggers it would be useful if you already know the unit IDs in question or can tell the range of possible unit IDs. That means that there are no other units dying/created than your "runners" you want to check for.

I do stuff and thingies... Try widening and reducing the number of small nooks and crannies to correct the problem.
Another idea: Now that ScmDraft supports unit IDs directly you could directly check for the unit ID instead of following it with a 1x1 pixel location. That would work for burrowing and flying units too.
But when you're not willing to make hundrets of copies of triggers it would be useful if you already know the unit IDs in question or can tell the range of possible unit IDs. That means that there are no other units dying/created than your "runners" you want to check for.
I fear that you didn't understand what the unit id means in the triggereditor. It's not the unit ID on the map. It's the general unit ID.
For the list, just press on the "+" next to the collapse in the post:
Collapse Box

0=marine
1=ghost
2=vulture
3=goliath
4=goliathturret
5=siegetank(tankmode)
6=tankturret(tankmode)
7=scv
8=wraith
9=sciencevessel
10=guimontang(firebat)
11=dropship
12=battlecruiser
13=spidermine
14=nuclearmissile
15=civilian
16=sarahkerrigan
17=alanschezar
18=alanschezarturret
19=jimraynor(vulture)
20=jimraynor(marine)
21=tomkazansky
22=magellan
23=edmundduke(siegetank)
24=edmundduketurret
25=edmundduke(siegemode)
26=edmundduketurret
27=arcturusmengsk
28=hyperion
29=norad2
30=siegetank(siegemode)
31=tankturret(siegemode)
32=firebat
33=scannersweep
34=medic
35=larva
36=egg
37=zergling
38=hydralisk
39=ultralisk
40=broodling
41=drone
42=overlord
43=mutalisk
44=guardian
45=queen
46=defiler
47=scourge
48=torrarsque
49=matriarch
50=infestedterran
51=infestedkerrigan
52=uncleanone
53=hunterkiller
54=devouringone
55=kukulza
56=kukulza
57=yggdrasill
58=valkyriefrigate
59=mutalisk/guardiancocoon
60=corsair
61=darktemplar
62=devourer
63=darkarchon
64=probe
65=zealot
66=dragoon
67=templar
68=archon
69=shuttle
70=scout
71=arbiter
72=carrier
73=interceptor
74=darktemplar
75=zeratul
76=tassadar/zeratul
77=fenix(zealot)
78=fenix(dragoon)
79=tassadar
80=mojo
81=warbringer
82=gantrithor
83=reaver
84=observer
85=scarab
86=danimoth
87=aldaris
88=artanis
89=rhynadon
90=bengalaas
91=cargoship
92=mercenarygunship
93=scantid
94=kakaru
95=ragnasaur
96=ursadon
97=egg
98=raszagal
99=samirduran
100=alexeistukov
101=maprevealer
102=gerarddugalle
103=lurker
104=infestedduran
105=disruptionweb
106=commandcenter
107=comsatstation
108=nuclearsilo
109=supplydepot
110=refinery
111=barracks
112=academy
113=factory
114=starport
115=controltower
116=sciencefacility
117=covertops
118=physicslab
119=starbase
120=machineshop
121=repairbay
122=engineeringbay
123=armory
124=missileturret
125=bunker
126=noradii
127=ioncannon
128=urajcrystal
129=khaliscrystal
130=infestedcommandcenter
131=hatchery
132=lair
133=hive
134=nyduscanal
135=hydraliskden
136=defilermound
137=greaterspire
138=queensnest
139=evolutionchamber
140=ultraliskcavern
141=spire
142=spawningpool
143=creepcolony
144=sporecolony
145=unusedbuilding
146=sunkencolony
147=overmind(withshell)
148=overmind
149=extractor
150=chrysalis
151=cerebrate
152=cerebratedaggoth
153=unusedbuilding5
154=nexus
155=roboticsfacility
156=pylon
157=assimilator
158=unusedbuilding
159=observatory
160=gateway
161=unusedbuilding
162=photoncannon
163=citadelofadun
164=cyberneticscore
165=templararchives
166=forge
167=stargate
168=stasiscell/prison
169=fleetbeacon
170=arbitertribunal
171=roboticssupportbay
172=shieldbattery
173=khaydarincrystalformation
174=temple
175=xel'nagatemple
176=mineralfield(type1)
177=mineralfield(type2)
178=mineralfield(type3)
179=cave
180=cave-in
181=cantina
182=miningplatform
183=independantcommandcenter
184=independantstarport
185=independantjumpgate
186=ruins
187=kyadarincrystalformation
188=vespenegeyser
189=warpgate
190=psidisruptor
191=zergmarker
192=terranmarker
193=protossmarker
194=zergbeacon
195=terranbeacon
196=protossbeacon
197=zergflagbeacon
198=terranflagbeacon
199=protossflagbeacon
200=powergenerator
201=overmindcocoon
202=darkswarm
203=floormissiletrap
204=floorhatch
205=leftupperleveldoor
206=rightupperleveldoor
207=leftpitdoor
208=rightpitdoor
209=floorguntrap
210=leftwallmissiletrap
211=leftwallflametrap
212=rightwallmissiletrap
213=rightwallflametrap
214=startlocation
215=flag
216=youngchrysalis
217=psiemitter
218=datadisc
219=khaydarincrystal
220=mineralclustertype1
221=mineralclustertype2
222=vespenegasorbtype1
223=vespenegasorbtype2
224=vespenegassactype1
225=vespenegassactype2
226=vespenegastanktype1
227=vespenegastanktype2
229=anyunit
230=men
231=buildings
232=factories


We can't explain the universe, just describe it; and we don't know whether our theories are true, we just know they're not wrong. >Harald Lesch
I fear that you didn't understand what the unit id means in the triggereditor. It's not the unit ID on the map. It's the general unit ID.
I fear you're right Ahli.

OK then use EUD triggers to refer to the unit. Shouldn't be too hard to find the unit ID with Farty's list.wait... this is not gonna work... There's no
easy way to detect if the unit is inside a location -- using unit ID, is there?