you need VBA to do it automatically, but if you many, many rows, then you can
use the following procedure to speed it up a little.
Say the first three columns are the first, middle, and last names, and you
want to join them with spaces inbetween. In D1 enter the following formula
=A1&" "&B1&" "&C1
the copy the formula down to the bottom of your data. You can then copy
column D and paste special (selecting values) to remove the formula and have
just data. You can then delete any original columns that you don't need
anymore.