Detect the last cell of AdvStringGrid

VCL TMS VCL UI Pack
1
I'd like to know the way to detect the last cell to move focus to the next control.
The last cell is the cell except for ReadOnly cell when Navigation.AdvanceSkipReadOnlyCells := true;

If cell B3 is selection and Enter key is pressed, 
I do not understand to move focus to a button on following sample application.

I use AdvStringGrid ver 8.3.8.0 and Delphi XE8.

Sample application
put a TAdvStringGrid and TButton on TForm1, and OnCreate event is below.

procedure TForm1.FormCreate(Sender: TObject);
var i:integer;
begin
    AdvStringGrid1.ColCount := 4;
    AdvStringGrid1.RowCount := 4;

    for i := 1 to AdvStringGrid1.ColCount-1 do begin
        AdvStringGrid1.Cells[i, 0] := Char(ord('A')+i-1);
    end;
    for i := 1 to AdvStringGrid1.RowCount-1 do begin
        AdvStringGrid1.Cells[0, i] := Char(ord('1')+i-1);
    end;

    AdvStringGrid1.Options := AdvStringGrid1.Options + [goEditing];
    AdvStringGrid1.Navigation.AdvanceOnEnter           := true;
    AdvStringGrid1.Navigation.AdvanceOnEnterLoop       := false;
    AdvStringGrid1.Navigation.AdvanceSkipReadOnlyCells := true;

    AdvStringGrid1.ReadOnly[3, 3] := true;
    AdvStringGrid1.Cells[3, 3] := 'RO';
end;

2

The Enter key will not move the focus to the next control.The enter key moves focus within the grid only.

There is currently not a built-in function to detect the last not readonly cell of the grid. You'd need to add the code to detect this at application level.