Button in Exit SAPMV45A Dynpro 8309 only for VA21/22/23

Hi,

ich use the above Exit with some Buttons and it works like i need.

Now we whant, that one of the buttons shell only be shown in Tcode VA21/22/23.

Today in PROCESS AFTER INPUT i check XVBAK-VBTYP with "B" to
realize, that the button can only be used in VA21/22/23.

I think i have to use any code in PROCESS BEFORE OUTPUT. Has anyone an idea?

Thanks

Regards, Dieter