Searcing for sale price for each old customers again and again

Searcing for sale price for each old customers again and again

Hi,

I need to look for old prices again and again for old customers. how do I know at what price I billed a particular item to repeat customers? Going to transaction each time is too time consuming. also we cannot have fixed price list as our prices to clients vary depending on duration, services and solution.
Kindly solve this.