Cross referencing to non Heading Styles

I am using Word 2003.

I have a long legal document which uses standard Heading 1 - Heading 8
styles throughout. I then have Annexure pages at the end, which are Annexure
A, Annexure B etc. These headings are formatted in a style called Annexure.

I now want to cross reference to the Annexure headings. The way I am doing
it is to insert a SEQ field for the A, B, C, etc and then bookmark the
headings.

Seems a little fiddly, is there a better way? I'm not "allowed" to modify
any of the Heading 1-9 styles as a matter of company policy.

Thanks.