Date Relationship Problem

Hello,

Despite reading a lot of material about this issue I am not able to achive the soluntion I require.

I basically have 2 key tables.  Sales information that include date and salesrep and a tabel containing monthly sales targets for salereps.  I require 2 types of analysis:  Sales information by salesrep against target and sales information for each salesrep per month against target.  I can achieve the first by creating a linking table of  Salesreps.  However I am not able to create a second linking table for months without making the link to Salesreps inactive.  Documentation suggests creating a copy of tables but I dont understand how this would work.

I would really appreciate help to solve this, since this must be a very common issue.

Thanks, Phillip