Calculating points based on Date, Document Number and Total Sold

Hi,

I have five fields - item, document number, date of sale, total sold, points total.

I want to calculate the points total.

Each item has a points total associated with it. However, if the product was purchased before 14/11/2012 it is given a single points figure and if it is purchased after it is given a double points figure. The single points and double points are named ranges. I want to multiply the total sold by the points for that item, depending on whether it is single or double - based on when it was purchased.

I only want the calculation to be performed for products that have a document number beginning with 2. If it begins with a 3 then I don't want a calculation performed.

Any help would be appreciated, attached is a sample of the spreadsheet.

Thanks

David