I've searched around a bit and haven't found an answer, so I'm a little nervous this isn't possible.
I've been adding interactive sort to row groups and it has been working just fine, but I'm getting stuck when I try to add it to a column group. For example, I have a row group called Agency_Ref and a column group called Nutrition.
In the nutrition grouping, the expression is =Sum(Fields!Weight.Value) / Sum(Fields!Weight.Value , "Agency_Ref") so that it displays the percentage of the particular nutritional attribute for the agency row grouping. When I add that expression to the sort by expression in interactive sorting, I don't get an error but the sorting doesn't work. It pretends to sort and just stays in the same order.
Any thoughts?