TextFlow: How to apply certain rules to it?

In my application I use the wonderful ability of WPRichEdit
to "link" a few controls together, so that the text can flow
from one to another in case it doesn't fit entirely. By using
this feature, I can do multi-column output in my reports, and
similar "split" functionality, like placing parts of the text
in separate blocks on different pages. (For those of you who
missed it - check out TextFlow sample).

Here is what I'm missing there: ability to affect the rules for
calculating the "break", i.e. the place in the document
where the split occurs. Currently, it is fully automatic, and
the break happens on the first line, which doesn't fit.

Here is a sample of the text, which demonstrates the need in
more intelligent rules:

Zitat

TITLE

Intro text. Intro text. Intro text.
Intro text. Intro text. Intro text.

Subtitle.
Some text. Some text. Some text.
Some text. Some text. Some text.

Subtitle.
Some text. Some text. Some text.
Some text. Some text. Some text.

Subtitle.
Some text. Some text. Some text.
Some text. Some text. Some text.

Alles anzeigen

I'd like to suggest to the engine somehow, that I prefer
break to happen on a "subtitle" line, so that it always
stays together with the subsequent paragraph(s).
This is just one example - in fact, there are different
cases like this, and they may have more complex rules.
So it'd be nice to introduce some "user-controlled" logic
there...

What's the best way to approach this?

Thanks!

Mik