How can I sum up some values per page in a table in XSL-FO?

I'm using XSL-FO to generate an account statement print out. The PDF is actually just a simple table with a simple header on every page. The difficulty is that I have to display transaction volumes per page, e.g.

Page 1

+------------------------------+-----------+-----------+---------------------+
| Text                         | Credit    | Debit     | Balance             |
+------------------------------+-----------+-----------+---------------------+
| Previous month               |           |           |           (*1) 1000 |
| abc                          |      1000 |           |                2000 |
| abc                          |           |       500 |                1500 |
| abc                          |           |       200 |                1300 |
| ...                          |           |           |                     |
| Carry over                   | (*2) 1000 |  (*3) 700 |           (*4) 1300 |
+------------------------------+-----------+-----------+---------------------+

Page 2

+------------------------------+-----------+-----------+---------------------+
| Text                         | Credit    | Debit     | Balance             |
+------------------------------+-----------+-----------+---------------------+
| Previous page                | (*2) 1000 |  (*3) 700 |           (*4) 1300 |
| abc                          |      1000 |           |                2300 |
| abc                          |           |       500 |                1800 |
| abc                          |           |       200 |                1600 |
| ...                          |           |           |                     |
| Carry over                   | (*2) 2000 | (*3) 1400 |           (*4) 1600 |
+------------------------------+-----------+-----------+---------------------+

Here are some explanations:

This is the previous month's balance. It's pre-calculated and well-known as an XSL variable. No problem with that, that's a regular header (only on the first page)
This value is calculated on a per-page basis. It sums up all credit amounts on the same page. I can't calculate that myself, as I don't know when XSL-FO will do the page break. So I imagine XSL-FO must do the calculation for me. The sum at the bottom of a page is the same as the value at the top of the subsequent page.
This value is the same as 2, only for debit amounts.
This value is just the last transaction's balance at the bottom of a page. That value is repeated at the top of the next page.

How can I do these calculations with XSL-FO?

Solution

Unfortunately, (at the time when I answered this question, it's no longer true) fop doesn't implement <fo:retrieve-table-marker/> from what I have found out. Instead, this solution here worked for me:

How to display one or the other information depending on the page number in XSL-FO?

It involves creating a separate table outside of the <fo:flow/> that displays the table header using <fo:retrieve-marker/> elements.