xpath (comparing?)

I've reworked my code to make what I'm doing easier, by creating two 
new virtual elements in the temporary tree: mods:refclass and 
mods:reftype.
However, I'm still stuck on the last part of putting it all together 
into a proper xpath  (2.0) expression.
So I need to modify the below based on this logic:

	-	if the mods:reftype=some value, and that value has an equivalent 
style definition (cs:reftype/@name='some value'), then use it
        -       if not, then default to "article" (which is required)

          <xsl:when test="mods:refclass='part-inSerial'">
	    <xsl:apply-templates select="$style-biblio/(for $t in 
$refclass-partInSerial
		return cs:reftype[not(@inherit-from)][(_at_)name=$t])[1]/(cs:* except 
cs:creator)">
              <xsl:with-param name="source" select="."/>
            </xsl:apply-templates>
          </xsl:when>

So at it's most basic: if mods:reftype='legal case' and 
cs:reftype/@name='legal case' exists, use it, etc.  What is my 
<xsl:when test=".."> statement?
Bruce