Automatic price update in billing level

Hello Experts,

My business require change pricing in condition record of  billing  level (without using update).

for example one sales order have 1000 quantity for one material .but delivery and billing we can use change in price time to time so problem is after change in condition record system fetch in billing level first price without using update .our requirement is system fetch automatic price without using update in billing level .

I go through lots of thread but not suitable  for my requirement.if any userexit  plz suggest me.

Thanks