drop down insert record on the fly

I have imported a table from excel using Navicat (which is itself a great mysql admin package) and have built a nice form very quickly with phprunner. Some of the fields in the imported table contain categories, one for example contains a list of countries. What I wanted to do when creating a new record is to have a lookup wizard drop down for the country field and have it already populated by the existing contents of the table (with Unique Values set). Just in case the user wishes to enter a country name that is not already in the table I clicked the option to allow that user to add a new country on the fly. However if this option is used, instead of adding the new country to the users record, a completely blank record is created containing the new country name and THEN a second record is created when the user saves the form. It seems that it should be possible to have the new country name added only to the users new record and NOT have a second record created. I know that I can create a second table with only the country names and have the lookup grab its data from there, but I wouldn't have thought it too difficult to have the whole thing working from one table?? This would be a great bit of functionality for people importing existing data and where in particular they wish to use lookup fields as an aid record input.