Maintaining a list of TIWFrames and descendants of TIWFrame

[ScottWGast]

I have a single form and many frames that descend from TIWFrame:

TIWFrame->TIWFrameBase
TIWFrame->TIWFrameBase->TIWFrameGRID
TIWFrame->TIWFrameBase->TIWFrameCRUD

TIWFrameBase includes some new properties and a few IW components
TIWFrameGRID includes ado dataset grid, controls, buttons
TIWFrameCRUD includes ado dataset, edit controls, buttons

and would like to store these varying TIWFrames in a collection where they can be
retrieved as needed.  The program will know the index of the desired frame and it will know the desired frame's type. 

My initial thought was to create an array of TIWFrameBase, but complained when I tried to insert a TIWFrameGRID into the array. 

My gut tells me that this should be super simple and I'm a little ticked off I can't figure it out, even with Google.

TIA for your help.
Scott