Pricing Rules- Product Volume with a Price Change

We REALLY want to use Pricing rules for the following scenario: Purchase 3 of the 12 performanes and you will recieve a discount. We would like the discount to be applied by a price type change. We have set this up as a Product Volume Rule with a Price type change. We have set it to Switch from a Reg price type to a new Fest Pass price type and have selected the 3-12 products (performances). We have added it to the Rule Set that is associated with 2 MOS. In both of those MOS nothing happens when we add 3 performaces at the Regular price type. We would expect that the price type would change to the Fest Pass price type that we programmed. What are we missing?

Thanks!

Janna