Hi Walter,
Snipped.
>1. Display changed data in red, non changes in blue.
>2. Normally the object is flat, when you enter the control, it becomes 3D.
>3. The all have logic to set a filter on the bound table based on the current value
>4. etc.
>
>In VFP there is no way to do this in a clean way other than having the (almost) the same code in all four classes.
>
We agree that IU controls should share certain behaviors. Our base classes have code like this:

IF NOT EMPTY(This.BehaviorType) 
   RETURN THISFORM.aBehavior[This.BehaviorType].txtGotFocus(This)
ENDIF

We have several behavior objects that consolidate the code. Our control base classes do almost nothing when their BehaviorType is set to 0, the default. If we set their BehaviorType to 1, we expect the developer was smart enough to drag a behavior object onto the form and call it Behavior1. If you want a group of controls to act a bit different, set their BehaviorType to 2, drag on a Behavior object, call it Behavior2, and add the code to it--in one place.
Behavior objects know to register themselves in the form's aBehavior array, so they are ease to call.