[xsl] limit the results of preceding in predicate

[Marc Lambrichs <marc.lambrichs@xxxxxxxxxxxxx>]

Suppose $tail is a nodeset of 'A' nodes:
<xsl:variable name="tail" select="//A"/>
All 'A' nodes have an attribute 'property' which contains a number.

Now I want to find the first 'A' node inside $tail that has a certain 
property ( in this case: the sum of all preceding  @property = 
$someNumber ).

If you use the following declaration just once, there's no problem.

<xsl:variable name="test" 
select="$tail[sum(preceding-sibling::A/@property) = $someNumber][1]"/>

However, if $tail is part of a recursion process and changes, how can I 
make sure that the 'preceding-sibling::A' are restricted to the current 
$tail nodes?

--
Marc