Cutom sort in matrix with grouping

Hi,

I have a matrix visual with 2 rows added for some grouping.

I would like to sort the 2nd level row based on the value on a column that is not used, rather than alphabetic. However, there is no column tab to allow any sorting on this matrix other than the usual alphabetic on the entire thing.

In this example below, it is the ordering of the City 1, 2, and 3 I would like to be able to change based on a column called Priority which has a number in it.

i.e.:

France

City 1

City 2

City 3

UK

City 1

City 2

City 3

Canada

City 1

City 2

City 3

USA

City 1

City 2

City 3