JasperSoft Studio Crosstab Total Calculation

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I've been experiencing some difficulty using the crosstab element in JasperSoft Studio:

I am displaying various data about specific stores' products, including stock levels, sales values as integers/floats, and gross profit as a percentage. The rows of my crosstab represent branches and the columns represent the relevant data pertaining to a product for each branch. The totals are correct for values such as stock level, since values like this one are simply summed and displayed. The gross profit percentage, however, presents a problem, in that I cannot simply sum up/count/average the individual percentages per product, per branch. Since my MySQL select obtains the relevant totals for me, I would like to use them directly. However, I cannot access my main dataset's fields from the crosstab.

I've spent hours trying to find a way to obtain the total gross profit percentage from my main dataset, but without success. The deadline for this report is looming, and I would really appreciate your help :(

In a nutshell, I want to display a field from my main dataset in my crosstab, without that field being a measure.