Drop down lists work just fine. What do you mean by "they don't work at all"? They don't work the same as a pop up menu, but they DO work as they have been designed to work and might well be better than a pop up menu for use here.
The simplest way (not necessarily the best way), is to use a pop up menu and in the value list set up, specify that it only show values from the second field. This will automatically show the doctor's name in the popup menu field once a value has been selected. Drop down lists do not do this, you have to use a different approach--I could describe two options here for that.
To get other data from the doctors table is simply a matter of having the correct relationship in place. If the ID field that matches Clients to doctors by doctor ID is the field that you've set up with this pop up menu, you can add any field, such as the doctor's phone number to the layout and it will update to show the doctor's number once you have selected a doctor in the pop up menu.
If you used a drop down list, you would use this method to add the doctor's name field to your layout--even placing it on top of the drop down list formatted ID number field, to show the name of the selected doctor.
And there is also a way to use an auto-complete drop down list of doctor names---not ID's to look up (copy over) the doctor ID into the ID field in the client record--but this method does require some scripting to pull off. The advantages though are:
a) you get a value list of names that auto-completes
b) the same script can manage two or more doctors of the same exact name where the other options require unique doctor names.
c) If you enter a new doctor name, the script can detect this and offer to create a new record in the doctors table.
Drop down lists, I was under the belief through experience and somewhere I read on a forum will NOT display the second field when doing a dynamic list that pulls from the Key+2nd field. It will only display the first field... whereas popups will. or am i wrong. Wont be the first time. :) thanks for the quick reply I am going to pour through what you wrote.