Frame and MDIChildFrame problem

[Reid Lai]

Hi There,

Is there anyone knowing how I can control the number of frame instance 
opened?  I have defined a "Open" menu item which opens another 
MDIChildFrame object.  But accidentally click this menu item twice while 
I expect one-and-only-one instance will be created.  And is there any 
same method to control inherit from wxFrame?  Thanks for any help.

Regards,

Reid Lai