If you use validation on the field, you can make it so that the vaule has to be a value from a set value list. You can also allow the users to override the validation.
This will probably be your easiest solution.
Thanks for replying.
I have no prior knowledge of scripting, so you can consider me a blank slate. I'm not sure what it means to "use validation." I think I understand how to get a script to become active when I want it to (script triggers). My main difficulty is actually writing the script.
No scripts involved. Go to your field under 'Manage Databases'. Double click your field and then go to the Validation tab.
Aha! That's fantastic. Exactly what I was hoping for. Thanks!