I'm having problems getting excel to do exactly what I need.
Ive got a demo column (shown below) that needs the values ST and S replaced with STREET, and the one currently with STREET to remain untouched. 

ASH S
SMITH STREE
BLACKSTONE ST
S. SOUTH ST
I've tried find and replace, and =SUBSTITUTE(A1;" S";" STREET")
But you can see why these won't work. The best example is "S. South St" where it will replace South with S. Streetouth Street. I somehow need to look for a string that has no characters following it. Any suggestions?

Thanks!