Dynamically controlling sort order based on values in

I have some xml that looks like :

<DISPLAY>
    <CONFIG>
        <COL>
            <ID>ColA</ID>
            <ORDERBY DIRECTION="ASC">1</ORDERBY>
        </COL>
        <COL>
            <ID>ColB</ID>
            <ORDERBY DIRECTION="DSC">2</ORDERBY>
        </COL>
    </CONFIG>
    <DATA>
        <ROW>
            <COL ID="ColA">
                <VALUE>BBB</VALUE>
            </COL>
            <COL ID="ColB">
                <VALUE>111</VALUE>
            </COL>
        </ROW>
        <ROW>
            <COL ID="ColA">
                <VALUE>CCC</VALUE>
            </COL>
            <COL ID="ColB">
                <VALUE>333</VALUE>
            </COL>
        </ROW>
        <ROW>
            <COL ID="ColA">
                <VALUE>AAA</VALUE>
            </COL>
            <COL ID="ColB">
                <VALUE>222</VALUE>
            </COL>
        </ROW>
    </DATA>
</DISPLAY>

I have a stylesheet that outputs the data sorted by the element in CONFIG
where COL/ORDERBY/text() is 1,  which looks like :

<xsl:template match="DISPLAY">
   <xsl:variable name="sort_col"
select="CONFIG/COL[ORDERBY/text()='1']/ID/text()" />
   <xsl:apply-templates select="DATA/ROW" mode="do_data">
      <xsl:sort select="COL[@ID=$sort_col]/VALUE/text()" />
   </xsl:apply-templates>
</xsl:template>

<xsl:template match="ROW" mode="do_data">
   <xsl:value-of select="COL[@ID='ColA']/VALUE/text()" />, <xsl:value-of
select="COL[@ID='ColB']/VALUE/text()" />
   <br />
</xsl:template>

This gives me :
AAA, 222
BBB, 111
CCC, 333

I need to be able to sort the data based on the CONFIG element of the XML
and I don't know ahead of time how many columns there are going to be in the
dataset and how many of them I will need to sort by.

Can anyone suggest a way to achive this ?

Thanks

Steve