How to Prorate only the first payroll deduction for benefit rates

Summary:

We have a requirement in which we have monthly payroll deduction and for new hires in middle of the month, the Benefit rate should get prorated for the first pay period only and normal rate should be applicable for the subsequent pay periods.

Content (please ensure you mask any confidential information):

We have a requirement in which we have monthly payroll deduction and for new hires in middle of the month, the Benefit rate should get prorated for the first pay period only and normal rate should be applicable for the subsequent pay periods. Any help on achieving this requirement would be much appreciated. Thanks in Advance.