I have two worksheets. One has a project Code with corresponding reference codes in the cell to its right. Altogether there are several hundred project codes and about five corresponding reference codes which match. (More than one project code can match a single corresponding reference code but only one corresponding reference code can match a Project code, one to many relationship.) In another table/worksheet I have a list of Project codes where the corresponding reference code fields are blank. How do I populate the corresponding reference codes into the second worksheet according to the first worksheet? Thanks.