TDrawCellEvent = procedure (Sender: PControl; Cnv: PCanvas; ACol, ARow: Longint;
    Rect: TRect; State: TGridDrawState) of object;

    private
// ..........
    procedure _onDrawCell(Sender: PControl; Cnv: PCanvas; ACol, ARow: Longint;
                    Rect: TRect; State: TGridDrawState) ;
// ..........
   public
// ..........
   end;
implementation

procedure THIStGrd.Init;
var tgo:TGridOptions;
begin
//.......
  Inherited;
  Control2.OnSelectCell:=_onSelectCell;
  Control2.OnDrawCell:= _onDrawCell;
end;

procedure THIStGrd._onDrawCell;
begin
// твой графический обработчик
end;