Grouping and Unique Lists

I've searched the archives and found a few posts in this area, but nothing
that seems to directly address the problem.  I'm working with the Microsoft
IE5 XMLDom.  Given the following XML:
<?XML version='1.0'?>
<ITEMLIST>
<ITEM>
<CATEGORY>Category A</CATEGORY>
<NUMBER>00001</NUMBER>
<DESCRIPTION>Item 1</DESCRIPTION>
</ITEM>
<ITEM>
<CATEGORY>Category B</CATEGORY>
<NUMBER>00002</NUMBER>
<DESCRIPTION>Item 2</DESCRIPTION>
</ITEM>
<ITEM>
<CATEGORY>Category B</CATEGORY>
<NUMBER>00003</NUMBER>
<DESCRIPTION>Item 3</DESCRIPTION>
</ITEM>
<ITEM>
<CATEGORY>Category C</CATEGORY>
<NUMBER>00004</NUMBER>
<DESCRIPTION>Item 4</DESCRIPTION>
</ITEM>
</ITEMLIST>
1.  Using XSL, convert to the following output (without using the actual
category name as part of the XSL)
Category A
00001 Item 1
Category B
00002 Item 2
00003 Item 3
Category C
00004 Item 4


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