Atypical list

As a beginner at XSL-FO standard I have a problem with a list (enumeration).
The thing is that the list in my XML document is not typical. It consists not
only of regular enumerated items but also has binsertionsb, which are
integral components of the list.

An example of such list:

<list>
  <item1>b&</item1>
  <item2>b&</item2>
  <insertion>b&</insertion>
  <item3>b&</item3>
<list>

In order to format such list, I can not use a <fo:list-block> element, because
a model of this does not allow insertions (like has been described above).
Hence, I think, bordinary textb should be used. And here is a problem. An
item of the list consists of a label and content. A content element can have a
quite complex structure and is wrapped in a <fo:block> element (<fo:block>
element can also appear repeatedly at lower levels of the list item
contentbs structure). The list item would be like this:

<fo:inline>
  <!bItem label here -->
</fo:inline>
<fo:block>
  <!bItem content here -->
</fo:block>

What should I do, in order to an XSL-FO to PDF processor does not break a text
line after the label?

Thanks in advance,
Konstanty.Pilecki