The problem you're running into is that once you call something outside of your EXE, that program, form, or whatever, can't call a form or class that's in the EXE. But there's good news--you can call a PRG or procedure that's in the EXE! So, to get around this, you need to create a generic procedure with a parameter that has the command to want to run (like "DO FORM MyForm WITH param1, param2"). Then you just need to macro expand the parameter:

FUNCTION RunCommand
LPARAMETER tcCommandLine

&tcCommandLine

RETURN