Variable Resource in PMAC

Dear All,

I have one business case in which a stainless steel pipe manufacturing industry uses some polishing wheel that are consumed as the steel pipes are produced. They consider those wheels as Resources and want the behavior of the resource to be variable depending upon the number of pipes produced in one run. This resource some times due to machine efficiency and human made changes in usage calibration used more in some pipes while consumed less in other pipes. Can anyone explain me how should I take this in the Recipe so that I can have a right consumption of this