Creating association with custom field in Linq2Sql

Question

Scenario

Table A: field_1 (with leading 0's, Ex. 125)

Table B: field_1 (no leading 0's, Ex. 000125)

What is the best way to setup my model in L2S so that I can have an association b/t the 2 tables by the "field_1" column? I basically need a way to create a custom property (or whole seperate entity) that I can perform a simple transaltion (in this simple example "0000" + field_1)