User exit on CO11 on system status MILE at 1st operation

Dear SAP Experts,

Please guide me which user exit to use on CO11, such that after putting rejection on ist operation , system status remains same as it was before putting rejection. Before putting rejection system status is PCNF ICHA MILE REL, and after putting rejection system status is PCNF ICHA REL. I want that system status remains same as it was before putting rejection. As when I save after putting rejection system status does not change,So please guide me with best solution.

Regards

Muhammad Umar