Hi,
In the same window this can be done.
Upload two images for two signatues say sign1 and sign2 as STANDARD texts in or better even as BITMAP images transparrent in nature. Then call these standard text in the window based on a condition say flag GV_FLAG which you can set in the code and print based on that.
Hope this makes it more clear or you want the IF ELSE logic block in SCRIPT.
Cheers,
Arindam