Metric and Formula Models to Calc PTO

I am new to LBP and just getting my feet wet. We would like for the PTO dollars to be calculated based on a % provided by users, then that PTO dollar amount be pulled out of the salaries total. If salaries and wages were $100,000 with 10% PTO, the result would be salaries and wages = $90,000 and PTO = $10,000. When we try to set this up we get a circular reference error.

Can we create sub-accounts that can hold the original salaries and wages total, then calculate PTO based on this and return the Salaries and Wages (less PTO) in the parent account and PTO in it's account? If we do this does it double the value of wages and Benefits or is there a way to hide this sub-account?

Any help would be greatly appreciated.