Interactive sort for a grouped table

I'm trying out the interactive sort feature (and have searched high and low for this answer), but can not make the sorting work if I have the data in the table grouped. If I remove the group, the sorting works fine but the output is not acceptable due to the duplicated records in the list.

Can someone steer me in the right direction?

I'm not really sure whether this is what you are looking for, but figured it is worth a try:

http://msdn2.microsoft.com/en-us/library/aa337431.aspx

See To add an interactive sort button on a group