type
THack=class(TcxCustomGridTableItem);

var C: THack;
    L: integer;

procedure TForm1.cxGrid1TableView1MouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
var H: TcxCustomGridHitTest;
begin
  H := cxGrid1TableView1.GetHitTest(X,Y);
  if H is TcxGridRecordCellHitTest then begin
    if (X > TcxGridRecordCellHitTest(H).ViewInfo.Bounds.Right-3)
      then cxGrid1TableView1.Site.Cursor := crHSplit
      else cxGrid1TableView1.Site.Cursor := crDefault;
    if C <> nil then C.Width := X-L;
  end;
end;

procedure TForm1.cxGrid1TableView1MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
var H: TcxCustomGridHitTest;
begin
  H := cxGrid1TableView1.GetHitTest(X,Y);
  if H is TcxGridRecordCellHitTest then begin
    if (X > TcxGridRecordCellHitTest(H).ViewInfo.Bounds.Right-3)then begin
      C := THack(TcxGridRecordCellHitTest(H).Item);
      L := TcxGridRecordCellHitTest(H).ViewInfo.Bounds.Left;
    end;
  end;
end;

procedure TForm1.cxGrid1TableView1MouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  C := nil;
end;