Converting from RH X5 for Word to RH 7 HTML - How to Map Word Styles to CSS Styles?

I have been using RH X5 for Word for years, and all my source docs are in Word.

Now, I want to convert to RH 7 HTML, where all my source will be converted to HTML docs.

I could have sworn there was a way to map my styles in my Word source docs to the styles in a custom CSS file I have, but I have not found how to do this yet.

Please help!

Thank you,
Marjorie