I have a large app that has been converted from 3.0b to 5.0a and I'm having a problem with help id's

We have created a base class for buttons derived from commandbutton that is used for all buttons in the application. In this class we've set the HelpContextID to =THISFORM.HelpContextID. That way when the button has focus and someone presses the F1 key, they should get help for the containing form. This worked fine in 3.0, but it fails in 5.0a.

When the instantiated button control inherits the default HelpContextID from the base class, pressing F1 produced the error "Expression evaluated to an ilegal value". If I override the default setting in the instantiated button control and replace it with the exact same text =THISFORM.HelpContextID, it works ok. If I go back in and "reset to default" using the right click on the property in the designer, it will fail again.

Anyone run intor this before or have any idea how to solve it. I don't want to override every single control in our application to place this text in there.
Thanks