Lookup settings - AJAX list or auto complete?

I need to create a field that

  1. Lookups a database table xxx
  2. Field “apple”
  3. Have the field provide suggestions as I type content in the field - so AJAX

N.B. There is no dependency on any other field. The list has 200 entries and needs to be updated regularly, so not practical for me to type and update every entry in a SELECT box.

How do I do this?

If I need to rely on AJAX Processing - it does not work…the options do not activate
Have tried auto-complete also. Same result