That displays the Listfield content. That isn't what I want, but thanks for the answer.
I think I need to clarify what I am trying to do.
The combobox uses a ListField called prov_name and this is a lookup list of province and state names.
The KeyField is called prov_code and is a lookup list of province and state abbreviations.
So, if the province name is 'British Columbia', and I click on British Columbia, the edit box needs to contain 'BC'.
Similarly, if the state is California, 'CA' needs to appear in the edit box.