Hi Sreehari,
If I understand your requirement this is vendor specific. There might be different vendors with different exempted values which is not advisable to create WHT codes for each requirement and the same might keep on changing every year. Is that correct? If yes, this was a gap in SAP solutions. And now SAP has recently released a note for this problem.
Please refer SAP Note 1945137. We are also in the process of implementing this note and not yet complete. This note is to meet the gap and we are not 100% sure how this is really going to work.
Have a look at the note and let us also know what you find.
Thanks,
Basavaraj