There are a couple of options.
- If you have a set of unusual words, you can add words using the ISpLexicon interface (or use the Windows Speech Recognition Speech Dictionary).
- Dictation recognition improves dramatically with context. You should callSetDictationContext as you update your recognition (and as the user changes the caret position).
- Last, you can use the Dictation Resource Kit to define a new dictation grammar. Only do this as a last resort, as it's a very complex process.