Detecting when drives are added or removed

BOOL CHelperFucntions::DoRegisterDeviceInterface(HWND hWnd, HANDLE hFile, bool bRegister)
{
	DEV_BROADCAST_HANDLE NotificationFilter;
 
	if(bRegister)
	{
		char szMsg[80];
		ZeroMemory(&NotificationFilter, sizeof(NotificationFilter));
		
		NotificationFilter.dbch_devicetype = DBT_DEVTYP_HANDLE;
		NotificationFilter.dbch_reserved = 0;
		NotificationFilter.dbch_nameoffset = 0;
		//NotificationFilter.dbch_data = NULL;
		//NotificationFilter.dbch_eventguid = 0;

		//This can be a file handle to the root of USB drive!
		NotificationFilter.dbch_handle = hFile;
		HDEVNOTIFY hDevNotify = NULL; //Perhaps this should be passed into the function by the caller?
		NotificationFilter.dbch_hdevnotify = hDevNotify;
	
		NotificationFilter.dbch_size = sizeof(DEV_BROADCAST_HANDLE);
		
		//hWnd is the handle to the main application window which will handle the incoming message.

		hDevNotify = RegisterDeviceNotification(hWnd, &NotificationFilter, DEVICE_NOTIFY_WINDOW_HANDLE); //or DEVICE_NOTIFY_ALL_INTERFACE_CLASSES

 
		if(!hDevNotify) 
		{
			wsprintf(szMsg, "Could not register to receive notifications about drive events: %d\n", 
				GetLastError());
			MessageBox(hWnd, szMsg, "RegisterDeviceNotification failed", MB_OK);        
			return FALSE;
		}
		return TRUE;
	}
}

	if (wParam == DBT_DEVICEQUERYREMOVE)
	{
		PDEV_BROADCAST_HDR pHdr = (PDEV_BROADCAST_HDR)lParam;      
		//When an USB drive is inserted or removed, we get DBT_DEVTYP_DEVICEINTERFACE and DBT_DEVTYP_VOLUME.
		switch( pHdr->dbch_devicetype ) 
		{
		case DBT_DEVTYP_VOLUME:
			{
				PDEV_BROADCAST_VOLUME pDevVolume;
				ZeroMemory(&pDevVolume, sizeof(pDevVolume));
				pDevVolume = (PDEV_BROADCAST_VOLUME)pHdr;
		
				CString csMP = "";
				csMP = cHF.FirstDriveFromMask(pDevVolume->dbcv_unitmask);
				csMP = csMP + ":\\";
 
				// This is a drive we are interested in
				// because we have registered to receive notifications
				// for this drive.
 
				int iRet=0;
				iRet = MessageBox("The user wants to remove the " + csMP +" drive. Allow?", "Device Removal Permission", MB_YESNO + MB_ICONEXCLAMATION);
				if(iRet == IDYES || iRet == IDOK)
				{
					//Figure why we are interested in this drive
					//Do whatever is necessary to clean up our act
					//If we could not find any reason why, just return true.
					lpReturn = TRUE;
 
				} 
				else 
				{
					lpReturn = BROADCAST_QUERY_DENY;//if not ready to unload USB
				}
 

				break;
			}
		}
	}

char CHelperFucntions::FirstDriveFromMask(ULONG unitmask)
{
   char i;
 
   for (i = 0; i < 26; ++i)
   {
      if (unitmask & 0x1)
         break;
      unitmask = unitmask >> 1;
   }
 
   return (i + 'A');
}