There is more than one collision being checked for in the function.
I originally had been using overlap, but overlap doesn't pick the colliding objects the way that colliding does, which hoses the rest of the script. It's an 'infection' type of script, similar to the 'evil sprite' demo.
Thank you both. I may have found a solution, though: Making the function enable or disable a group, and within that group is my script. The function also initializes some variables necessary for the script, and checks to see if the group is still running or not, returning an error if it is. This should get close enough to being able to use the script as if it were a true function. I'm debugging it now.