BPS 0QUANTITY 4 Decimals

I have a Measure (%) that is tied to 0QUANTITY and I need it to go to 4 places after the decimal. 0QUANTITY is set up to go 3 places after the decimal. My only thouhgts are to create a custom key figure that looks like 0QUANTITY, but with 4 decimal places. Then tie that to my measure in the layout?

Any other ideas?

Thanks, Keith Johnson