If I understand you correctly, for a specific WT, you need to compare the results between the Original Payroll Results and the Recalculated Payroll Results for that same pay, and not between the Last Payroll Results and the Current Payroll Results.
Please confirm for what Country Code your requirement applies as what you refer to should be a standard functionnality.
Also confirm if your "Social Insurance" Deduction is a Standard Technical WT or a Custom WT.