Changing (First Name Middle Initial Last Name) to (Last Name, First Name Middle Initial)

I need to change a row of data from "John X Doe" with no period after the initial to "Doe, John X" - Thanks, just can't figure out how to deal with the middle initial. Also, some names don't have middle initials, so the standard formula that I have now works fine on those, just can't process the middle initial yet. Thanks!