user exit for ME51n (purchase requisition)

Dear All,

i want to use user exit for transaction ME51N i have found a user exit named MEREQ001 and there are around 10 different exits EXIT_SAPLMEREQ_001 to 10

but the problem is i want to have a check for plant with costcentre now thing is that i m getting plant in table IM_DATA_PERSISTENT of user exit EXIT_SAPLMEREQ_005

but i not getting costcentre anywhere can anyone plz help me out

if this is not possible than is there any other alternative by which i can apply check between plant and costcentre for transaction ME51N (purchase requistion)