ways to use position()

Can anyone please tell me whether there are other ways touse position()
apart from position=1?
I tried the following:

<xsl:variable name="qNum">
<script>
function getQuestionNumber()
{
parent.qNo;
}
</script>
</xsl:variable>

<xsl:template
match="Categorydefs/CategoryDef/QuestionDefs/QuestionDef[position()=$qNum]"
xml:space="preserve">
<FONT><P><xsl:value-of select="@Caption"/></P></FONT>
</xsl:template>

but the browser says that I can't use variables this way...  arre there any
other ways to change the number of position?

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list