CFileDialog - Double clicking files

I would be very grateful if you could help me with a problem.

I am using VC++ and CFileDialog. I have some extra controls on the dialog.

When double clicking a file, before closing the dialog i want to perform some of my own validation. The problem is i cannot find a way of catching the event after double clicking a file. I cannot use OnFileNameOK() because this gets called everytime i try to close the dialog.
I am closing the dialog using GetParent()->SendMessage(IDOK);

Any help would be much appreciated.