MS Word changes my caption field codes when I insert a new caption - can I stop it?

I have a document with a heading style for the main body (the standard Heading 1, Heading 2, etc., in a numeric multilevel list, e.g. section 1.2.3.4), and a heading style for the appendices (named AppHeading 1, AppHeading 2, etc., in a multilevel list with the first style a letter and the rest numbers, e.g. section A.2.3.4).

When I caption a figure in the main body, and include the chapter number, I get automatic styleref and seq fields,

Figure { STYLEREF 1 \s }-{ SEQ Figure \* ARABIC \s 1 }

In the styleref field, Word finds me the name of the most recent style 1. Apparently Word has it hard coded in that 1 means "Heading 1". The \s in the styleref field strips out any non-incremental text from the chapter name (if it was "Section 2.", I'd get just "2").

In the seq field, Word returns the next number in the sequence named Figure, formats it as an Arabic numeral (1, 2, 3, etc, as opposed to a Roman numeral or an ordinal number like 1st, 2nd), and resets the numbering at heading level 1.

So for the third figure in section 2, I get Figure 2-3. Which is exactly what I want.

But in the appendix, my "chapter number" and the sequence reset should be from "AppHeading 1". That's easy enough to change in the styleref field. There's no apparent way to do that in the seq field, though, so I'm forced to insert a Heading 9 style on the title page of my appendix and use

Figure { STYLEREF "AppHeading 1" \s }-{ SEQ Figure \* ARABIC \s 9 }

Which gives me Figure A-3, and that's great. A little kludgy with the Heading 9, but I'm not too bothered by it.

What does bother me, however, is that if I insert a new Figure caption anywhere in the document, Word automatically changes all my appendix Figure captions to

Figure { STYLEREF 1 \s }-{ SEQ Figure \* ARABIC \s 1 }

Is there a way to prevent Word from resetting my fields? Thanks in advance! (And, while you're at it, if anybody can suggest something to prevent my Heading 9 kludge, I'd appreciate that, too!)