How is dwCookie being used...?
invoke CreateFile,gofn.lpstrFileTitle,GENERIC_WRITE+GENERIC_READ,\
FILE_SHARE_WRITE+FILE_SHARE_READ,0,CREATE_ALWAYS,\
FILE_ATTRIBUTE_NORMAL,0
mov [edi.MdiStruct.hFile],eax
invoke GetLastError
invoke MessageBoxA,0,str$(eax),0,MB_OK
mov EditStream.dwCookie,eax
mov EditStream.pfnCallback,offset StreamOutProc
invoke SendMessage,[edi.MdiStruct.hEdit],EM_STREAMOUT,SF_TEXT,addr EditStream