StringGrid右击选中表格（发消息给句柄模拟点击，右键点击也是MouseDown）

procedure TFGLGL.StringGrid1MouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
var
MousePos:   TSmallPoint;
begin
if   Button   =   mbRight   then
begin
MousePos.x   :=   x;
MousePos.y   :=   y;
SendMessage(StringGrid1.Handle, WM_LBUTTONDOWN, 0, MAKELONG(x, y));
SendMessage(StringGrid1.Handle, WM_LBUTTONUP, 0, MAKELONG(x, y));
end;
end;