Setting cells Read Only

This sounds silly, I can't make a simple operation work! I need to make a cell read only, thus I set it :

Grid1.ReadOnly[1,10]:= true as the property of the grid; yet it is still editable !! What did I miss????

The grid properties (in full) are set as the followings:
Grid1.FixedRows := 1;
Grid1.FixedCols := 1;
Grid1.ColWidths[0] := 20;
Grid1.Options := AdvColumnGrid1.Options + [goRowSizing, goEditing, goColSizing, goColMoving];
Grid1.MouseActions.RangeSelectAndEdit:= true;
Grid1.ReadOnly[1,10]:= true; 

//to set col 3, row 3 and row 5 Read Only
procedure TForm1.Grid1CanEditCell(Sender: TObject; ARow, ACol: Integer; var CanEdit: Boolean); 
 CanEdit:= not (ACol in [3]) and not (ARow in [3,5]);

Everything works as expected except cell[1,10] IS NOT READ ONLY. HELP please.

Can't be reproduced with a standard grid on the form with the latest version of the TAdvStringGrid and following code:

 procedure TForm1.FormCreate(Sender: TObject);


AdvStringgrid1.RowCount := 20;

AdvStringGrid1.FixedRows := 1;

AdvStringGrid1.FixedCols := 1;

AdvStringGrid1.ColWidths[0] := 20;

AdvStringGrid1.Options := AdvStringGrid1.Options + [goRowSizing, goEditing, goColSizing, goColMoving];



AdvStringGrid1.MouseActions.RangeSelectAndEdit:= true;

AdvStringGrid1.ReadOnly[1,10]:= true;



Please note that default the grid has only 10 rows, you have to define the rowcount first before you set cell [1,10] readonly. 

I did define the rowcount before setting the cell[1,10] to RO. I'll send you (tmssupport) the full project to reproduce the problem. Thanks Nancy.