I doubt that this has anything to do specifically with a Maryland tax return. You should be filing part-year returns for both Virginia and Maryland. On each you will identify what portion of your income was earned while a resident of each state. Assuming that your W-2s include both income earned while a Virginia resident and income earned while a Maryland resident, you should see on the W-2 state tax withholding for both Virginia and Maryland. You should see each state's tax withholding credited on the corresponding state tax return. I haven't specifically looked a preparing a Maryland part-year tax return, so I can't provide much more in the way of details.
Note that Maryland and Virginia have reciprocal tax agreements, so whether your employer was in Maryland or in Virginia, your employer should have been withholding state taxes for the state in which you were a resident at the time that you earned the income. If the employer was not timely notified of your change of state of residence or simply failed to withhold taxes for the correct state, you'll get a refund of any excess taxes paid to one state that you'll then use to help cover any underpaid tax liability incurred in the other state.
