What problems are you facing creating a new variable and specifying a value/formula to be the product of the two variables ? Any error ?
To expose the new variable and use in Draft, you can read this article:
To use a exposed variable in the BoM, select the BoM in Draft, Open its properties by right-clicking it or from the Command Bar, then take the Columns Tab.
In the list of Properties, you will find the exposed variable which you can add as a column.
Find attached a PDF document I discovered a long time ago that has helped me do magic with Solid Edge.
Find also attached a parametric ordered part model of a truss which should be an ample example on using formulas within the variable table with boolean logic as per the PDF.
Add your own user variable name by starting on the bottom left cell and go on from there. Learn how to use the display filter and table ordering to quickly find stuff.
I hope this helps you.