Need to disappear Close button of Panel on docking

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Delphi

I don't want that users can close the panel by pressing the 'X' button on the top-right corner.But... when the panel is docked, a little 'x' appear on the corner of the panel, is there a way to hide this little button?

I have tried code on create dock panel, but it is not working

procedure Tframe1.panBorderEndDock(Sender, Target: TObject; X,  Y: Integer);
 var
   hMenuHandle : Integer;
   begin
     inherited;
     hMenuHandle := GetSystemMenu(panBorder.Handle, False);
     if (hMenuHandle <> 0) then
     DeleteMenu(hMenuHandle , SC_CLOSE, MF_BYCOMMAND);
   end;

Kindly check my code and give some suggestion Please.?