PO Release Strategy

Hi All, Hope someone can help. I have created a new po release strategy. I have added the field to CEKKOZZ, I have included the logic to populate the field (KSCHL - Condition) in the user exit. I have included a new charcateristic and Class. From testing it seems that the populated field is not being passed back up the chain from the user exit although another previously defined field is working ok. Any suggestions? your help very much appreciated - cheers terry