COGNOS - sorting a crosstab with nested rows

[MrTy]

My crosstab has nested rows, say location, region and product and a measure gross unit sales.

US, South, nine iron, 2500
US, Far West,nine iron, 1400
UK, Scotland,nine iron, 900
UK, England, nine iron, 1800

What I want to do is sort the entire crosstab on gross unit sales.  So the crosstab appears:

US, South, nine iron, 2500
UK, England, nine iron, 1800
US, Far West, nine iron, 1400
UK, Scotland, nine iron, 900

So far, I have been unable to get this kind of sort in place.

Any tips or suggestions are most welcome.