choosing the window to send the events

[Alfonso]

I'm writing a program that should simulate key events in a given window.
I have achieved that using XTest. The question is, is there some way to
avoid that the simulated key events propagate to other windows? The
events are send to any window that the mouse pointer is placed on. I
would like to be able to make those events only occur on a concrete
window, and not, that for, example, when I leave the program in
execution and open a terminal, the simulated key pressed are send to the
terminal instead of the window that they should be send to.

In advance, thank you very much for your help and advices.