I am building a database that calculates prices for products.

I generate the products by specifying the materials I need the quantity of this material the unit price of the materials. The price of material changes each month and thus I generated a new field that incorporates the material number with additional parameters of year and month. For example:
Material LFRGP-PLA-G1S-0/1-AS-10
Will be called LFRGP-PLA-G1S-0/1-AS-10-2003-SEP
I have a table that has all the unit prices for the materials sorted By month year (they are all in one table).
The problem I have is to auto populate the Unit Price for each material once I have generated the material code with the Year and month parameters added to it. e.g.
Material Code Unit Price
LFRGP-PLA-G1S-0/1-AS-10-2003-SEP $1.25
MDFBD-COM-G2S-1/4-PG-25-2003-SEP $ 1.56
SLDWD-ASF-RLB-4/4-PG-56-2003-SEP $3.44
If anyone could help with this problem it would be most appreciated.