I have a request to sort columns by the summary value of the column and not the value of the rows used in calculating that summary.

 Example.  Columns are grouped by Type ascending and sorted by Number ascending.  This would be default grid behavior:

Type       Name            Number

 Dummy 1                       25     <-summary value for number

              Name 3             10

              Name 4             15

 Dummy 2                        8

              Name 1              1

              Name 2               7

However with my sorting I would like it to appear like this:

Type       Name            Number

 Dummy 2                        8

              Name 1              1

              Name 2               7

 Dummy 1                        25

              Name 3             10

              Name 4             15

Where would I begin to implement something like this?