may be this will help
may be this may solve your problem..
UPDATE tblTempUsers INNER JOIN concate ON tblTempUsers.UserName = concate.[Concatenate 1st & 2nd Name] SET concate.UserID = [tblTempUsers].[UserID];
SELECT tblUsers.ID, tblUsers.UserFirstName, tblUsers.UserLastName, tblUsers.UserID...