nice problem i want to solve it but i don't have time, so, what do you want?, to create a managed MDI app, and put in it unmanaged MDI childs? or just to interact with unmanaged forms?

check this out, is not much but is something:

http://www.ondotnet.com/pub/a/dotnet/2003/01/20/winformshosting.html
,
http://msdn2.microsoft.com/en-us/library/ms229600.aspx,
http://www.ddj.com/documents/s=9698/ddj0505l/0505l.html,
http://groups.google.com/group/microsoft.public.dotnet.general/browse_thread/thread/5e047dae5c467269/069c400c68572aac?lnk=st&q=Hosting+Win32+Forms+in+Windows+Forms&rnum=4&hl=en#069c400c68572aac,
http://www.opennetcf.org/PermaLink.aspx?guid=905b2ec3-b8ae-4e65-bb22-7e7545d31816,
http://groups.google.com/group/microsoft.public.dotnet.languages.csharp/browse_thread/thread/f7c5c0b7d5a84f6e/2e44e0a565015ca8?lnk=st&q=Hosting+Win32+Forms+in+C%23+Apps&rnum=1&hl=en#2e44e0a565015ca8,