Tvheadend

I succesfully managed to setup tvheadend with my iptv provider. I also managed to find out how I can get the EPG working using the webgrabplus-module. But using that method, it takes pretty much time to add all the channels in the xml files.

Since my iptv provider also gave me an EPG-url, using format http://xxxxxx/xmltv.php?username=12345&password=12345, can someone point me out how I can integrate this in TVheadend? I just can’t find out how the external xml grabber works.