uses comobj;

procedure TForm1.Button1Click(Sender: TObject);
var
 XL : variant;
 x:integer;
begin
 XL := CreateOleObject('Excel.Application');
 XL.WorkBooks.Open('c:\Êíèãà1.xls');
 XL.Visible := true;

 for x:= 1 to XL.ActiveSheet.Shapes.Count do
 begin
  if XL.ActiveSheet.Shapes.Item(x).Name = 'Check Box 1' then
  begin
    XL.ActiveSheet.Shapes.Item(x).Select;
    XL.Selection.Value := false;
    break;
  end;
 end;
end;