Update employee salary retroactively without losing benefit enrollment data

We have many employees who need to have a salary change with an effective date that is prior to the date of their latest benefits open enrollment record.  When I update the salaries using HR_MAINTAIN_PROPOSAL_API.INSERT_SALARY_PROPOSAL api with a change date from last year, the benefits enrollment from this year gets lost.  I was wondering if there is a way to update these salaries in bulk without losing any data after the salary change date.