Transferring And Copying Data From One Cell To Another Using Formula?

I have a database with different categories assigned to employees. I wan't to do the following. I will use just as an example, I want to some how accomplish: If Cell A in worksheet 1 equals cell C in worksheet 2, then replace Cell L in worksheet 2 from cell b in worksheet 1. Basically we have a database with phone numbers with corresponding purchase codes for each phone number and their names. The problem is, all the purchase codes are incorrect on the spreadsheet. We have an updated spreadsheet with just phone numbers and no names. I need to somehow pull the proper purchase code from one worksheet to the old document replacing the old purchase codes.