I assume you are talking about the totals that show when using 'partial sums'?
How about rather than using the expression:
you use instead:
if (rowno() <> 0, sum([number ordered])
where in this context rowno() returns the row number in the current column segment and so is 0 when its a total line.
If you have partial sums at the lowest dimension level (ie you have a 'grand total' line) and you want to suppress that too use instead:
if (rowno() <> 0 and rowno(TOTAL) <> 0, sum([number ordered])