You should be able to use a wildcard Find/Replace, where:
Find = (. )([A-Z])
Replace = \1 \2


or:
Find = (.) ([A-Z])
Replace = \1 \2
or:
Find = (.)( [A-Z])
Replace = \1 \2
Find = (. )([! ])
Replace = \1 \2
and so on. None of these is capable of producing 'One sentence.A nother sentence.' There is also no need to complicate things with extra parameters or escape codes.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Today it works. I have often used wildcard find and replace successfully, including the situation I described. The day I posted I was getting the erratic results. I spent some time on it before posting, as I was sure I had missed something. All I can say is that I am certain I was doing it as I described, with the result I described, but now it works as expected.

"As a 'wild card', [A-Z] will only match one single uppercase character."
That was my intent. I was looking for a period followed by a space followed by any upper case character. The Find highlighted that combination. I realize there are abbreviations and other situations where I would not want the extra space, so I was stepping through the document and replacing as appropriate (except I was sidetracked by the the oddity that appeared that day). I had restarted Word, but got the same result. I didn't try a computer restart, but I should have done so before posting. I have seen oddities appear temporarily with Word and other Office products (and not limited to MS programs). All I can think is that this must have been one of those.

Anyhow, thanks for the replies. I appreciate both of you taking time to respond.