Deriving Existing controls to a new base class.

I'm developping some grid control and I would like to automate the edition
with any control placed on that grid and linked to a field.
It will be direct editable on the grid transparently to the user.

The Main problem is to set and get the value for all those control to be
uniform. My idea is to create new components : TCWListBox, TCWEditBox, and
that all. But they should have a new base Class : TCWWinControl that should
add 2 Methods, SetValue and GetValue. I don't know if it's possible, but any
suggestion is welcome.

Thanks :-)