[Zope-dev] External method

This is not a strictly zope related question but it is zopeish :) In an external method I need to call an executable and capture the output it generates. This executable however needs to connect to a running X Server. I used the popen2 command but it returns with the obvious error : "theprogram : cannot connect to X Server". So how does one tell a program to attach to a X server? Any help would truly delight me Roché