>Already on it's way --- bear in mind that this is proof of concept. Also, I forget to say in the email, you set the controlsource at design time as you would any other bound control. The control itself swaps out the CS and maintains the value and the updating of the controlsource source value.
>
Let me take a wild guess here. You put something in the INIT like:

This.AddProperty('cSource', This.ControlSource)

Then in the Refresh:

This.Value = eval(This.cSource)

In the LostFocus:

replace (This.cSource) with This.Value

You, of course, probably dressed each method code to test for existence, etc.