How to change revenue recognistion relevance for the Item cateory

Hi,

I have gone through the sap notes 1166848, inorder to change the Revenue recognistion relevance from the standard to the service-related revenue recognition (revenue recognition type B) using T.code OVEP, however i am still facing the same issue that the field is uneditable. Is there anything is should do before i can make changes to the same. We are planning to test the Revenue recognision in our sandbox.

Thanks in advance for quick support.

Br,

Sridhar