SAP HR US BENEFITS QUERY

Hi Experts,

This question is related to SAP HR US Benefits. Currently in 170 infotype FSA we have provision for employee to choose a different plan at any point of time but now the new requirement is If employee had already enrolled in to one plan the system in FSA should not allow him choose another plan or even if employee selects another plan then he should not be picked in Payroll.

Can we do this in standard or any user exit is required for this?

Please let me know the solution so that I can do it accordingly.

Thank you all in advance for your help.

Regards,
Vamshee