How do I control the units an equation evaluates t

I am using a weldment part to generate multiple strips of EVA foam for use as padding in a higher level assembly. The strips do not require individual part files, and are cut from a large stock of sheet. I need to create a variable that can be used in the BOM of the assembly drawing to show how much of the material is required each time one of these assemblies is built. The variable should have the same UOM our supply department has assigned to the sheet--in this case it is sq-in. I can get the number I need simply by dividing the volume (i.e. SW-Volume) of the part(s) by the thickness of the sheet stock (i.e. the respective dimension for thickness shown in the custom weldment profile of the strip's cross section). I created the equation, but the units are inches instead of sq-in, and I cannot find a way to change it. Solidworks does not seem to understand that multiplying two of the same units together raises the exponent. Is there a way to control this?