Get the lowest PB00 price

Hi,

I'm facing an issue in my current project, the requirement  is to get the lowest PB00 price in my MM pricing Schema, for exemple :

  if i have 40USD for the table Product/Vendor/Site and 45USD for the table  Product/Vendor/Group_Site, then the system schould give 40usd and not 45 even if the right sequence is  Product/Vendor/Group_Site.

Thank you in advance,