This article should explain why this doesn’t work.
https://bobj-board.org/t/15226/18
As for the computation error, make sure all the dimension objects required to calculate the measure are in the report. Computation errors occur when a dimension used to calculate a measure is missing.
Can you be more specific as to what the error message is or what is happening when you try to perform the calculations?
csurguine (BOB member since 2005-01-04)