the "sebrpc" reference made me think of the 'Nam Pack, where there's this one soldier who is a radio man. I suppose that's what you're using, right?
Anyway, as far as I can tell the actual radio doesn't do anything, and it's used for exactly the kind of stuff you're planning on using it for
However, since it can't fire and doesn't have any ammunition or any other way to check if you're "using" it, you better just add a little extra condition to that waypoint...i.e, after using the radio (as in the radio menue, which is what I suppose you're using), you just add a line like, usedRadio=true at the back of the script or on Activation line, and then put usedRadio in the condition field, making it look something like:
aP hasWeapon "sebrpc" AND usedRadio
:-) that should solve your problem. If this wasn't your problem, please elaborate a little bit more
G'luck!
Wolfrug out.