ML81N - CUSTOMISED FIELDS IN DISPLAY MODE

My requirement is to add certain custom fields in T-Code ML81N. For this I am using the Enhancement SRVEUSCR - User screen on tab strip

I have added the fields in Table CI_Essr. and then mapped these Custom fields in the Screen Exit on Screen 0399. The custom fields have appeard on the Tabstrip.

But the problem is even if I am viewing the line item in ML81N in Display mode, my custom fields are appearing in editable mode. And if I am entering the values in the

if Any one Already worked on this Please Help  me

                                                                                                                                                          Thanks in advance