Hi Ian,
Maybe you can try it this way:
1. In 1st Tcode, "Paste Value" of your result into a hidden field on the Personas init screen.
2. Now do 2nd Tcode: first, "Copy Value" of the hidden field into a var, myVar.
3. In a script button, call the Tcode to go to the new screen, then do "Paste Value" of myVar into the field you want.
Does this help?
Dong Zhu