You should put this kind of code in access and assign methods. You can create code whenever you access or assing a value to a certian property. By putting the code in the assign method you can have that code change the value of your other property. Access and assign methods can be created by checking the checkbox when you create the properties or going to the edit properties window and changing it there.

ASSIGN METHOD for ThisForm.plTest should read:

LPARAMETERS vNewVal
IF vNewVal
ThisForm.pcTest1 = 123
ELSE
ThisForm.pcTest1 = 456
ENDIF
THIS.success = m.vNewVal

Put the default value of pcTest1 to 456 . Access and assign methods are only supported by VFP6.

Greetings,
Juri