Creating descendant from TStringField

Hi all,

I'm trying to write a descendant from TStringfield to add some
functionality I need.
Unfortunately Delphi always tells me, that it expects the connected
field to be from type TStringfield and not from the new, inherited one
and tries to correct it.
Is it possible to add new TField types to Delphi and how?

TIA
  Ruediger
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Ruediger Hoppe
r...@edit.de
Ruediger Hoppe
r...@edit.de