Lock Some fields of PR through ABAP Code

Hi,

there is simply a script wherever erstwhile the PR is created successful SAP, it volition beryllium sent to 3rd Party exertion for Approval via IDOC.

I americium looking for a anticipation to fastener immoderate fields of PR done ABAP Code based connected immoderate tract successful 'Status' tab astatine Item level until this Approval is implicit and this effect is received backmost to SAP via IDOC.

I mean Locking present successful the consciousness that the Fields should beryllium greyed retired and should not beryllium allowed to EDIT

The fields I privation to fastener are :  1. Fixed vendor astatine Item Overview Level

2. Quantity astatine Item Level

3. Gross Price astatine Item Level.

What are the possibilities of these ?

many Thanks successful advance