concatenate and delimiters redux

All,
Someone was good enough to solve my initial problem, many thanks! It was being able to concatenate a list of names with commas between names.

The resolution was:

=Substitute(Trim(E13&" "&E14&" "&E15&" "&E16&" "&E17&" "&E18&" "&E19)," ",",")

This worked great until my boss said "I want first and last names. Now someone whose name makes the list is shown as john, smith.

I am pretty new to Excel - any assistance is appreciated.
Thanks (again)
goji