等MDI的子窗体完全显示后，用ShowModal显示另外一外窗体，怎么实现？谢(50分)

等MDI的子窗体完全显示后，用ShowModal显示另外一外窗体，怎么实现？谢

if not Assigned(MdiChildForm) then
MdiChildForm:=TMdiChildForm.Create(Application);
MdiChildForm.Show;
if not Assigned(ShowModalForm) then
begin
ShowModalForm:=TShowModalForm.Create(Application);
ShowModalForm.ShowModal;
ShowModalForm.Free;
ShowModalForm:=Nil;
end;

？？？
这有什么技术难度？、看不懂