XSLT- Counting value based on duplite clientID

[richardt]

Hello,
I got a question, as I'm not sure what is possible,
I'm setting up a page based on XSLT where I can see orders with Value ready to be send out to the client
I build in a function that if a order had a bigger value than 10K then a line manager has to approve,

This works,
But now the question I need to implement also a function that if 2 orders from the same client ID are above 10K that this needs to be approved,

So in short I need to create a selection on Duplicate client ID then do Total + total is $totalsum.

Now I don't have a clue where to start.

I found something which can make me start.
where I replace Surname with clientId and Firstname with total.

<xsl:key name="contacts-by-surname" match="contact" use="surname" />
<xsl:template match="records">
	<xsl:for-each select="contact[count(. | key('contacts-by-surname', surname)[1]) = 1]">
		<xsl:sort select="surname" />
		<xsl:value-of select="surname" />,<br />
		<xsl:for-each select="key('contacts-by-surname', surname)">
			<xsl:sort select="forename" />
			<xsl:value-of select="forename" /> (<xsl:value-of select="title" />)<br />
		</xsl:for-each>
	</xsl:for-each>
</xsl:template>

But is this a right approach, I don't ask you to write a script, only advise me on a direction How To :).

Thanks Richard