Getting the cell clicked on in a TGridPanel

I have a TGridPanel on a form and wish to add a control to a specific "cell" that is clicked on.

I can get the point easily enough:

procedure TForm1.GridPanel1DblClick(Sender: TObject);
var
  P : TPoint;
  InsCol, InsRow : Integer;
begin
  P := (Sender as TGridPanel).ScreenToClient(Mouse.CursorPos);
  if (Sender as TGridPanel).ControlAtPos(P) = nil then
    begin
      InsCol := ???;
      InsRow := ???;
      (Sender as TGridPanel).ControlCollection.AddControl(MyControl, InsCol, InsRow)
    end;
end;

I probably don't need the if ControlAtPos(P) = nil then line, but I want to make sure I'm not inserting a control in a cell that already has one in it.

So... what code do I use to get InsCol and InsRow? I've been up and down the TGridPanel and TControlCollection class code and can't find anything that will give me a column or row value from mouse coordinates. Nor does their seem to be a relevant event to use other than OnDblClick().

Any help would be greatly appreciated.

EDIT: Changed variable Result to MyControl to avoid confusion.

procedure TForm1.GridPanel1Click(Sender: TObject);
var
  P: TPoint;
  R: TRect;
  InsCol, InsRow : Integer;
begin
  P := (Sender as TGridPanel).ScreenToClient(Mouse.CursorPos);
  for InsCol := 0 to GridPanel1.ColumnCollection.Count - 1 do
  begin
    for InsRow := 0 to GridPanel1.RowCollection.Count - 1 do
    begin
      R:= GridPanel1.CellRect[InsCol,InsRow];
      if PointInRect(P,R) then
      begin
        ShowMessage (Format('InsCol = %s and InsRow = %s.',[IntToStr(InsCol), IntToStr(InsRow)]))
      end;
    end;
  end;


end;

function TForm1.PointInRect(aPoint: TPoint; aRect: TRect): boolean;
begin
  begin
    Result:=(aPoint.X >= aRect.Left  ) and
            (aPoint.X <  aRect.Right ) and
            (aPoint.Y >= aRect.Top   ) and
            (aPoint.Y <  aRect.Bottom); 
  end;
end;