That may not work without a little modification. If the expression is sum(A)/sum(B), for instance, the sums won't work without doing an explicit aggregation. Adding aggregation across the three dimensions would be one solution, but since we have three dimensions, I'd think we'd be adding it to all three, which is an unweildy solution even if it would work. It would be simpler to apply this approach to the expression instead of the dimensions:
if(your_expression>0.05,your_expression)
And make sure that zero values are suppressed.
