Why not concatenate the cells? Perhaps you could find some logical criteria to sort the IP addresses into ones that should be made private, then concatenate...

For example:

Column A has the IP address
Column B has the word "Private"

In column C enter the following formula =A1&" "&B1
Your result would give you what you are looking for.

If the only word you will use is private than just enter this formula into column B:

=A1&" Private"