Populating options for drop down list

Question

I have a list that I will have users enter data into, each user needs to select their own location. First I created a drop down field with all the options. The column can be set to force unique values, but this doesnt check until the end when the user goes to save.

Is there a way to check if the users selection is already entered, immediately when the option is selected? (without having to hit save)

OR

Another option I tried was:

1. Create a separate list with two columns: name and saved. Call it Location_List
2. Create a view that displays all where saved = no on Location_list
3. Populate the options on the mainList from a look up the the Location_List. This works.
4. Add a workflow action to mainList that updates saved = yes on the Location_List. This part doesn't work. Does sharepoint allow this though?

Is there an easier way to accomplish this?

Answer 1

My second option worked, had simply forgotten to update the workflow setting to "Start automatically when item is created" for it to run accordingly.