You can Find the capitals that being any word with:
Find = <[A-Z]
There is no Find expression that will locate only capitals that begin a sentence. You can find capitals that begin a paragraph, via:
Find = ^13[A-Z]
but be aware that, if you use a replacement expression with this, it will apply to the preceding paragraph break as well. Anything more spohisticated requires a macro.

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