I have a query with [Which County?] as its Criteria. So it's already asking the user for the county it's to filter its results by.
I would like the input box that the user types the county name into to be a list box or combo box. Otherwise, I see a lot of typos being a regular annoyance.
Use a list box whose control source is a table that only contains the options you want the user to select from. There should be a table relationship between the table with the available country options and the table with the field you are filling in the form.