<?xml version="1.0" encoding="utf-8"?>
<root>
    <item>
        <val>10,1</val>
    </item>
    <item>
        <val>20,2</val>
    </item>
    <item>
        <val>30,3</val>
    </item>
</root>

<msxsl:script language="JScript" implements-prefix="baator">
<![CDATA[
    function test(N) {
        //processing result tree fragment N here, for example i need to convert //item/val to numbers and return a complicate f(N)
    }
]]>
</msxsl:script>
...
<xsl:value-of select="baator:test(//item)">