Oh, you were looking for solutions here? In that case, read on.
Believe it or not, there is actually a pronunciation editor for the Text to Speech utility called UserDicEng. It's not part of the Captivate interface and you aren't likely to stumble upon it accidentally. If you have installed Captivate and the Adobe Captivate Voices, you'll typically find the tool in the following location: Program Files (Windows) or Applications folder (Mac) > Adobe Captivate Voices > VT > The Agents Name > M16 > bin > UserDicEng (app or exe depending on your platform).
You can always click Read to hear the pronunciation of the new target word. When finished, click the OK button.
Click the File Save button followed by the Close button and you're done. The new pronunciation will be used by your Speech Agent within Captivate the next time you convert text to speech.