Montana Non Resident Online System Mistake/Omission?

Help! On Turbo Tax online I completed our federal tax form, then I moved on to Montana State Non Resident (which you are instructed to do before our Resident Idaho state tax).  However, the program prompts you to put in your income that was made in Montana but then never asks what tax we already paid to Montana.  We have a separate W2 just for Montana which shows how much income was made there and how much tax we already paid Montana state.  I looked on the Montana paper form and basically Line 21, where you can enter how much tax was already paid, is not covered on the online program making it result in a bunch of tax due.  Help!!