Present two delayed sound to the same audio-slave

Hi


I'm looking for advice on how to present two speech signals to the same audio slave-handle, but delaying the onset of one of them. I want one speaker to start and after between 3-4 seconds (varied randomly) the other should begin in the same channel as the other. 

I could do it 'manually' by adding the two signals with one being time-delayed, however I really what the trigger the onset-time of the seconds, as well as the first, speech-stream. Is there any way of adding a second sound to an already-playing buffer?


Does anyone have some experience with this?

Eline