Is there any program for Broodwar that randomly chooses a map from a set folder? This would be epic.

Chooses and does what with it? Because just selecting a random filename is can be done in excel:
run cmd and enter the following command in the folder with your maps:

dir /w > maps.txt

This will create a file named maps.txt that has one line with each map name. You may want to delete the overhead at the first and last few lines.
Open this file in Excel and enter the following formula into B1:

=INDIRECT("a"&(ROUND(RAND()*ROWS(A1:A???);0)))

where ??? is the number of lines (=number of files).
Every time you modify any cell (even press del in an empty cell) it outputs another map name to B1.