Restriction fields in IW32

Dear All,

I want some solution to my problem have searched many discussions but of no use. The requiremnt is in tcode: IW32, the users should not be able to change the main work center field and WBS field in IW32. Only one person should be allowed to change these both fields. How can i achieve this. Is this possible with authorization?? or any user exit is available for the same.

Regards,

Priti.