Hi Leroy:

Thanks for chipping in with this advice. The problem is actually to do with instantiation/z-order and setting the properties of one control based on the values of another. Through the day, I have messed around with this. The VFP help makes it very clear what the error message means. When the form was an SCX, the reference to Thisform from within a control was OK, even when the controls were initialising. When I modded the form to be a VCX, it was then instantiated in/by another (containing) class and therefore, the constructing class containing control(s) self-referencing "Thisform" violated VFP's containership rules.

The simplest answer I came up with that works like a charm is to test the value of the control's bound source (ie., the data value), as opposed to the control's value. This keeps the line between the interface and data nice and clean.

It always amazes me what can happen in a day and how much you can learn about a tool that you use all the time.

Thanks again for your advice!

Best