Yeah, that's what I tried at first but it doesn't seem to work!
Okay, I made two triggers. Each with a radio message, one is the initial message and the other is a reply.
The initial message trigger gets no delay and the reply trigger gets, let's say 15 sec.
However, when I call the Radio Alpha that both triggers are connected to, both messages sound at the same time, completely disregarding the delay I gave the reply trigger.
I know it can be solved (sort of) by placing a "present trigger" along the route of the recieving unit but this gets messy really fast, so if anybody can think of another solution please bring it on!