Checking if a player is in a certain steam group

Hey, i was wondering if its possible to check if a player is in a certain steam group WITHOUT actually looking at their steam profile. I was looking at gm_steamworks (http://www.facepunch.com/showthread.php?t=823783) although i have no idea how to use it, and yes i have looked at the examples it still confuses me. If someone could show me a way to do this with steamworks or something else it would be great! Thanks.

http://steamcommunity.com/groups/groupnamehere/memberslistxml/?xml=1 will output all of the groups member as their community ID.