Problem with Dynamic Running Heads Using Markers

Hi,

I'm having problems with using markers to generate a dynamic running 
head. I have a document that contain multiple articles and I want to 
create a header that shows the first article title that appears in the 
page (including carryover) and the last article title that appears 
within the page separated by an em-dash. However, when a page contains 
only one article, I want the header to show only one article title.

I have created markers for each article title:

<fo:marker marker-class-name="header-start">first</...>
<fo:marker marker-class-name="header-end"></...>

<fo:marker marker-class-name="header-start">second</...>
<fo:marker marker-class-name="header-end"> - second</...>

<fo:marker marker-class-name="header-start">third</...>
<fo:marker marker-class-name="header-end"> - third</...>

and retrieve them using:

<fo:retrieve-marker retrieve-class-name="header-start" 
retrieve-boundary="page" retrieve-position="first-including-carryover"/>
<fo:retrieve-marker retrieve-class-name="header-end" 
retrieve-boundary="page" retrieve-position="last-starting-within-page"/>

But using this, my header for a page that contains only one article (ie 
article second) was "second - second" but what i want is only "second".

Is there any way to test if in a certain page contains only markers from 
the same article? Or is there way to test the values of the markers that 
i retrieve?

Thanks,
-- 
*Jeff*