I want to do a report on a particular product sku, but the calculated metric builder uses hit level segments which don't work with merchandising evars.

Example:

I want to know what percentage of sales are gift wrapping.  In Workspace I can add a filter on Product, which brings back the correct table. But if I try to make a calculated metric, it automatically creates a hit level segment, which then includes all products in the order that had gift wrapping:

Is there a way to do a calculated metric which will look at just the units based on the values in the merchandising evar, rather than the hit level?

Thanks

Ben