asterisk users - Nov 2004 - please help !! - context for an incoming call

Hi everyone could somebody help me on this problem ???

I have a tdm04b card with 4 fxo's connected to 4 POTS of a media
gateway. Suppose that I want to place the following calls:

Zap/1 dials Zap/2 (by placing in /spool/outgoing a call file which
dials a number corresponding to Zap/2)
Zap/3 dials Zap/2 (also placing another call file)
Zap/4 dials Zap/2 (also placing a call file)
In each situation Zap/2 will enter its incoming context
defined in zapata.conf.
My question is if it's possibile to change at runtime the context that
Zap/2 uses? ( Zap/2 to enter different contexts depending on the
originator of the call)
Any help will be very much appreciated !!
Thank you all for your time..