multiplying columns in a Pivot table

Hello:
I have a Pivot table, with which I am trying to calculate a weighted average of Daily Rate prices.

I am basing the weighted percentage against Invoice Total, which is a copy of the Sum of Invoice Total field, but expressed as a percentage of that total.

What I want to do next is to multiply Daily Rate by Weight to come up with a column Weighted Daily Rate within the pivot column. I am trying to create a custom calculated field, however Weight does not appear in the list of fields, because it is based on the Sum of Invoice Total.

Is there another way to multiply two columns of a pivot table together while having that new field be part of the Pivot table?

Or, is there another way I could write an equation in the custom calculated field area?
Thanks much!

Thanks for the tip, Alan. Last night I was working with Chat GPT on that, and it had trouble getting me an accurate result. For some reason, it is not able to subtotal the invoice amount correctly. I may start a new thread.