Sorry for question.. I found. program() function had supported both of programs and forms...A different way to do this is in the called form's Load() method. When the called form is LOADing, the _Screen.ActiveForm is still the calling form, so code like this in the called form's Load() will also do it:
loCaller = _Screen.ActiveForm
IF VARTYPE( loCaller ) = 'O'
.
.
.
ENDIF