Hi Jagat,
Sorry, I did not understand your question.
What I suggested was to use the WSP and modify the detail_chg.htmpl file and wherever you have the custom configuration item field in the form (as per your screen shot, just after the "CAB" field) with the above lines - like below:
<PDM_IF "$args.id" != "" && "$args.status" != "RFC">
.... You will have your configuration item line here .... add "make_required="yes" like I have shown above
</PDM_IF>
Now:
"$args.id" != "" - means the value of the attribute args.id is not null.
Do not worry about that, just type as I have mentioned.
Thanks,
Indrajit.