How would I create a sub-form that is not visible with out command (command button, etc) and inputs the unique identifier. For example, when I track chemotherapy, most often patients are given multiple courses. I would like to be able to have a command button that would "add a new course" the sub-form would pop up and the medical record number of the active patient record in the parent table would be the default for the medical record number in the treatment table.

Any help will be greatly appreciated!