Do you have a max quantity number? The one way I can think of to do this will only work if that max quantity is not too large.
1. Create as many detail sections as the max quantity number.
2. Put the same fields/format in each of the detail sections.
3. In the suppress formula for each detail section, but something like the following:
<X> <= {table.quantity field}
Where <X> is the number of the details section (1 for section A, 2 for section B, etc.)
I'm not sure what the max number of sections for a report is, but I just verified that you can put more than 26.
-Dell