How to Multiple 2 fields

Hi Everyone,

So I'm trying to modify the sales line table (37) to add a field I named "Total Net Weight"... All I would like it to do is take field 35 "Net Weight" and multiply it by the "Quantity" field 15 and display on my new field...

I first tried to set my new field to be a FlowField and use CalcFormula to summat the lines but I really don't think this is the proper way to do it. Can anyone provide any guidance?

Thank you