Don, of course the BEST way to go about this is to set up a form with each of your 3 foreign keys as COMBO BOXES where you pick a value from a list. Now, if you are entering new records and a doctor isn't on the list in the combo box, then you need to add that record first. The EASY way to handle this is to close the current form, add the doctor on a doctor form, and then re-open the main form.

You CAN set up a combo box that will allow you to enter a doctor by typing in his name, and if he's NOT on the list, have Access prompt you to ADD him to the list. This, unfortunately, will involve some VBA programming using the OnNotInList event. I do cover it in my Access 324 Advanced class.