Person ID in Concurrent Employment

Hi there,

am trying to set up the concurrent employment in a group where employees have several contracts with many company codes within the group and consequently they have many personnel numbers however I cannot generate the Person ID which is the unique identification for each person. I set the switch in T77S0 to

CCURE PAUIX X CE Master Data User Interface Enhancements

but when I try to set the switch is teh entry CCURE PIDGN the fiels is greyed out and I cannot select from the list.

Is there a prerequisite that I should have done beforehand?

Can anybody help?

much appreciated!!!!

elli