I have never made an NPC like this but ill give it a shot:
this would be for like a DJ Booth:
NPC Code:
if (playerchats && strequals(#g,DJ)) {
setstring server.radio,#c;
}
this would be for all of the other radios:
NPC Code:
if (created) {
timeout=.05;
}
if (timeout) {
setcharprop #c,#s(server.radio);
timeout=.05;
}
Like I said im not sure if this will work.