During the calendar year, when an employee works for multiple companies in multiple states, what is

We have several employees that change companies and move to different states during a given calendar year; we need some guidance for employee and year-end setup and processing of the respective state W-2's.

 

Example: In 2013, Mary worked for company 100 in PA January – March and in AL April –September, then changed to work in company 200 in October with a move to CO; therefore, she worked in 2 companies and 3 states during the year. Her Resident State is CO (06). I understand the Home State can override as the Base State for W-2 tax reporting, but how can we generate the required 3 state W-2’s for Mary?