A user interface extension allows data entry into a marking machine user interface field from an electronic device, such as a PDA, attached to the marking machine via compatible communications ports. The marking machine includes a UI field into which data must be entered, the user lets the machine know that data will come from the electronic device, and the machine begins monitoring its communications ports for the data. The user enters or selects data to be transmitted from the electronic device, then indicates that the data is ready to be sent, at which point the electronic device transmits the data to the machine via a communications port of the electronic device.