uneditable column within editable row ?

hi friends,,,

i am using oo alv to display report..

in that report..

i maintained EDIT bt in the application Tool bar using PF-Status..

if i press EDIT bt the entire grid( key fields and other fields) become editable..

but my requirement is i want all the key fields uneditable.and remaining fields editable if i press EDIT bt.

thanks in advance