I have to make a purchase cube. The problem is that one purches is save in 2, 3, or more registers. Ex:

Purchase One:
Purchase CostCenter U$S
1 CCALM 10
1 CCADM 5
1 JURIBA 15

The value of JURIBA is CCALM + CCADM.
The problem is that if this is the fact table, and i want to view purchase one, the sum is 30, and that is wrong.. the real value would be 15. How can i resolve this problem? any idea?