Is there a table method that will calculate union dues that can calcualate the 'lesser of the two' w

We are on E1 9.2 and have to calculate union due as follows:

Looking for guidance on the following requirement.    the delivered table methods do not seem to have an average rate calculation that I might be able to adapt.

I need this calculation

Take the lesser of the two:   gross period wage X a percent   vs. Average hourly rate for the period X a factor

Thanks