Hide SAVE button during approval of a Shopping Cart

Hi Experts,

My requirement is to Hide SAVE button of the shopping Cart only when an approver opens it.

During all other sceanario, it should not be changed.

I have tried the below coding and it works fine if i give name of other buttons like 'EDIT' or 'ORDER'.

But it is not working for SAVE and CLOSE button.

"Hiding SAVE Button during Approval mode
     lo_cnr_oif->define_button(
         EXPORTING
           iv_variant_id  = 'VARIANT_SC_PROF'
           iv_function   =  if_fpm_constants=>gc_button-alternate_function
           iv_element_id  = 'SAVE'
            iv_enabled    = ''
           iv_visibility = cl_wd_uielement=>e_visible-none ).

Can anyone tell me the reason why it is not working? Also, tell me the correct way to hide SAVE button.

Thanks,

Parthi