How do you avoid getting an automatic space after your autocorrection?

Hello, another question for some brilliant mind out there! In Word 2007, how do I avoid getting a space behind my autocorrection, such as if I want to use the word at the end of a sentence, or followed by a comma or "? This has bedevil'd me for so long, and I would be so grateful for an answer, even if it is "no, it cannot be done." Thank you so very much! Donna T.