Одно событие на все комбобоксы
Код:
procedure TForm1.ComboBox1Change(Sender: TObject);
var m:integer;
begin
for m:=0 to ComponentCount-1 do
begin
if (Components[m] is TComboBox) then
(Components[m] as TComboBox).ItemIndex:=(Sender as TComboBox).ItemIndex;
end;