OTBI Payroll Reporting - How to Generate Employee Data as of Payroll Period & not Current Date

We currently have an OTBI report using the Payroll - Payroll Balance Real Time subject area. Currently, if we run this report it pulls in the employee Business Unit as of the date running the report. We added Advanced SQL Clauses in Prefix for SET VARIABLE PARAM_EFFECTIVE_DATE ='@{P_DATE}{@{system.currentTime}[YYYY-MM-DD]}'; so that we can utilize P_DATE to pull in as of effective date. However, even when I change the P_DATE to the Payroll Period Start Date it doesn't change the Business Unit field for the employee. It still defaults to the employee's current Business Unit and not as of the payroll period.