Add "Price" field with different values for specific timeranges

Hi,

I'm adding a "Price" field to each product in the events. Therefore I'm using a lookup which includes the productname and the price.

| lookup Pricelist.csv productname OUTPUT price

Is there a way to add different prices for specific timeranges? For Instance, Product A had a price of 5.00 until 24.11.2013, but for events >=25.11.2013 I would like to have a value of 3.00 in all events including product A.

Perhaps using a second lookup in combination with something like "if _time>=X lookup Pricelist2.csv productname OUTPUT price"?

Thanks in advance