Math calcs on custom group in Query Studio?

[Lisa]

Does anyone know how to do an arithmetic calc on a custom group in Query Studio? When I define the custom group, Query Studio thinks it's a text value, even though I'm defining the groups as numbers (950, 1450, etc.). It only lets me do string calcs (concat, 1st or last chars) on the custom group and I can't get to the math calc options. I'm trying to avoid creating a report in Report Studio, if possible. I'd really appreciate any advice.