Exclude certain rows from the grand total

[smac1979]

Hi!

I need to exclude some rows from the totals that SSAS do.

Letra Factura Valor
1 1 100
2 200
3 300
Total 600
2 2 10
Total 10
5 5 20
Total 20
Grand Total 630

What I want is to have only the sums of the "Facturas" equal to "Letra", but preverse all the "Facturas".

Letra Factura Valor
1 1 100
2 200
3 300
Total 100
2 2 10
Total 10
5 5 20
Total 20
Grand Total 130

How can I do this in MDX, or in SSAS 2005?

Thanks,
Sérgio Cardoso