APpendig structure

hello friend's

I am trying to append the structure in the stabdard structure KOMPEBA :

When i try to add the field BEDNR :

and check it : its gives error

first it is asking for Enhencement catagory

second : Field BEDNR does not lie in customer namespace :

i can't change the fieldname :

Because i have to refer this field in run time :

Plese help how canm i go ahead with this :

I am assuring i will awarded the points once i get solution .

Thanks in advance