Numbering

I have a table with Employees, and the month and year they started. I need to number them in order of the month and year they started. Example: July 2001 is employee 1 and August 2001 is employee 2. However there may be multiple employees in a given month and year. It seems like this should be a simple task but I can not figure it out. I have a query that puts them in the right order but not sure how to update the ID with the correct number. I'm using Microsoft Access 2002.

Thanks

TheAceManPlease post that query. Also, what are the data types for month and year?sql