Jeff,

Kind of a tricky business.  Please refer to
http://www.shaunakelly.com/word/numbering/OutlineNumbering.html for in-depth
guidance.

Regards,
Chad

You'll get a head start if you select the third pane in the bottom row on
the Outline Numbered tab (the one that has I. Heading 1, A. Heading 2,
etc.).

Under format and then style, make a new style (call it
something). Ensure it is 'based on' Heading 1, 'Style for
following paragraph' is Heading 1, and the 'style type' is
Paragraph.
Go to Modify > Format > Numbering> Customize
Change number style from 1,2,3 to A,B,C for level one.
Then click OK. On the screen behind tick add to template
and click ok. Then click apply. You should have you A
heading now.

Then make another new style based on the one you have just
made.
Ensure it is 'based on' Heading 2, 'Style for following
paragraph' is Heading 2, and the 'style type' is Paragraph.
Go to modify>format>numbering>customise again
Change number style from 1,2,3 to I,II,III for level two
this time.
Click on ok > tick add to template and ok > apply

You should now A.I

hope this helps. I know that this may make your previous
work revert to these new styles. ensur that in the
numbering you click the start numbering again radio button
and have section breaks between your document sections.