Sounds like an ASP.NET newsgroup question to me, not C# language.
Try here if you want to use the MS web interface:

http://msdn.microsoft.com/newsgroups/default.aspx?dg=microsoft.public.dotnet.fra
mework.aspnet&lang=en&cr=US

Peter

It's not entirely clear how your user is getting into the situation in  
which the wrong window is activated when the dialog box is dismissed.  
However, sometimes it's as simple as just making sure that the parent of  
the dialog box is set correctly, by passing the reference to the form that  
_should_ be the parent of the dialog box in the constructor when creating  
the dialog box.

If that doesn't correct the problem, then you will probably have to come  
up with a concise-but-complete code sample that reliably reproduces the  
problem, along with instructions for how to get the problem to occur.  The  
behavior you're describing isn't normal absent any other interactions with  
other applications by the user.

Pete