Im kind of confused on what it is you are even trying to accomplish? Do you want to run the .exe on the citrix machines or on anything besides the citrix machines?

The below code will run the .exe if the machine is not one of the listed and if the user is in the GN3_Users group.

Code:
If @WkSta<>"ChCitrixDS" and @WkSta<>"ChCitrixA" and @WkSta<>"ChCitrixB" and @WkSta<>"ChCitrixC" and @WkSta<>"ChCitrixD" and @WkSta<>"ChCitrixE"
   If InGroup ("GN3_Users")
      Run "\\gn3cluster\gn3\globals\gn_progs\update32.exe c:\tera\bin \\gn3cluster\gn3\globals"
   Endif
Endif