Different SMARTFORMS from FPR3

Hi all. I need to print 3 differents smartform depending on what kind of correspondence is generating from FPR3.

By now, I have copied the IS_U_CA_INSTPLAN_SF app. form wich is generated for an specific type of correspondence. But now I need that, since the same trx I can select a different smartform but not adding a new parameter to the IMG, but calling it from the exit on the app. form.

It's just a question because at last, I don't know if the deffinitive option is to create another app form and configure it on the IMG.

Thanks in advance.