[ContraVeneno]

No, no, no... yo me refería a que usaras el parámetro "Sender"

Código Delphi [-]
TForm1.OnEdit1Change(Sender: TObject);
begin
  if (length((Sender as TEdit).Text) > 0) then
        Button1.Enabled := true;
  else
        Button1.enabled := false;