Condition Exclusion : User Exit for Condition exclusion procedure update

Hi Experts,

I need your advise, to update an User Exit to change Condition Exclusion Procedure based on certain criteria :

Example :

Based on combination of Various Field, system should take Best condition between condition types or Least Favourable condition between condition types.

If above rule can not be satisfied, system should Ignore, Exclusion Procedure.

Now to achieve this and to update Field T684S - KAUVF, which specific User Exit in Pricing should I use and at what point of time.

Thanks in advance.

Regards,

MJ