I assume there could be more than one unit that sets off this mine? Like, any unit, or any west unit, etc? In that case, the solution, as usual, lies in some of my own work
. Check out my "find units" function
here.
To get the function to work, you will need one trigger to cover the whole mission area though (to catch all the east or west units).
The function just returns an array of every unit within X distance to another object. So in your case, all you would need is a loop that looks like this:
#enemyCheck
? count ([_MINE, 25, east_units] call findUnits) > 0 : goto "DETONATE"
~3
? alive _MINE : goto "enemyCheck"
exit
Where east_units is an array of all east units, found by putting something like this in the activation field of a trigger (activation: east present; covers entire mission area):
east_units = list this
Read the description of the linked function for more info.