How to create new table style based on an existing table

I'm working with Word 2003 on Windows XP Professional SP2

I tried starting with "New Style..." under Styles and Formatting to create a
custom table style and failed miserably.

So, I just insterted a table (FileTableInsert), created table heading and
table cell paragraph formats for it. Then, I used Table Properties to format
it exactly the way I wanted it.

Now, I want to save all that formatting as a new, custom table style and
make it the default table style for this document. Can I do that, and if so,
how?

Thank you.