So, there is an event called
"Unit enters range of unit" and the triggering unit is referred to the first unit parameter.
In a shoter game, I added all bullets in a unit group and tried to do something like
"Any unit enters range of any unit in unit group" but apparently, something like this does not exist, does it?
Please post a solution, no clues or hits. I want a tested solution.

Info:
Every bullet is owned by the same player and is the same unit type.

All I have been able to come up with is a system that will work in a region, and hit the closest unit to the trigger unit.
... I am trying to get it just so you can click and it will just shoot and hurt what ever it hits, but that is a bit hard lol.

Do you want my trigger for the hit closet unit?

( and why are you putting the bullets in a group.. is there a reason for that, or are you just trying to figure out how to get them shooting? )

Actually the group doesn't matter and was created for a test before.

That is what I figured!
If you download my rpg wasd system on the map productions. It has my system its not exactly what you want but you should still look at it and get some ideas.
Currently I am working on a system with a Depot / and I just want it to shoot photon cannon missiles at where the mouse is and hurt the unit near it. So I will also share what I find with you because I think We both are trying to make similar systems.

If you're trying to make a shooting system, you really need to get into ray tracing. Move a point a set distance each loop of your shooting trigger with polar offset of the yaw of the player's camera, alter the height of the point each loop relative to the horizontal distance traveled, pitch of the camera, and ground height, and check if the bullet hits stuff by seeing if it's below ground level or if there's a unit close to it. I have semi-working bullets and launched grenades (I say semi-working because for some reason, they change height when the ground does), if you'd like to look at my code.

Err, that's what I done. Camera aiming like in counter strike.
However, how did you manage the y-axis? how to order a unit to a height point?