once you write your query concatenating the first name and last name fields together, you could make a form, add a command button to the form, and behind the command button include some VBA to export the query results as an ASCII file. Something like this would work
DoCmd.OutputTo acOutputTable, "tblTemp", acFormatTXT, strExportFileName, -1
(When I export from MS Access I use a "report extract" temp table to hold the data prior to exporting it. I find that exporting from a table is less problematic than exporting from a query. In my example, tblTemp is the name of the temporary table that holds the data I am about to export. strExportFileName is a string variable previously defined in my VBA module that lists the name I want the exported text file to have. If you do not want to use a string variable, you could hard code whatever file name you would like your exported file to have provided the exported file name was surrounded by quotes. The -1 argument tells the computer to automatically open the exported text file once it is created. Using a 0 instead of -1 would instruct the computer to just create the text export file and not open it.)