Disabling Delete button from service attachement of ME53N

Hi All,

I am working on a requirement where i need to disable DELETE and ATTACH icons of ME53N-->Services for Object-->Attachment List.

These two icons should be made in display mode for the Purchase Requisitions which are released.

I tried creating a z authorization object and the copying the standard class CL_GOS_SRV_ATTACHMENT_LIST and further assigning the custom class in SGOS transaction.

This method didn;t give me the solution.

Has anyone worked on such requirement ?????

Please let me know your tips for this requirement.....

Regards

Pavan