<?xml version="1.0" encoding="utf-8"?>
<Man schemaVersion="1">
    <version>2.2</version>
    <file>
        <properties>
        …
        </properties>
        <group>
            <properties>
        ...
            </properties>
        </group>
        <group>
            <properties>
        …
            </properties>
            <group>
                <properties>
                    <items>
                        <name>test</name>
                        <description>A test</description>
                    </items>
                </properties>
            </group>
            <group>
                <properties>
                    <items>
                        <name>test2</name>
                        <description>A test field again</description>
                    </items>
                </properties>
            </group>
        </group>
    </file>
</Man>

<group>
        <properties>
            <items>
                <name>test3</name>
                <description>one more field</description>
            </items>
        </properties>
    </group>

<group>
        <properties>
            <items>
                <name>test</name>
                <description>A test</description>
            </items>
        </properties>
    </group>
    <group>
        <properties>
            <items>
                <name>test2</name>
                <description>A test field again</description>
            </items>
        </properties>
    </group>
    <group>
        <properties>
            <items>
                <name>test3</name>
                <description>one more field</description>
            </items>
        </properties>
    </group>

$strXMLfile="c:blablabla.xml";
$xml=get-content $strXMLfile;
$xmlRoot=$xml.get_DocumentElement();
$xmlnode=$xmlRoot.file.group;
$group=0;
while (!($xmlnode[$group].properties.name -eq "test node")) {
    $group++
}
$nodesGroups=$xmlnode[$group].group;
if ($nodesGroups.count -eq $null) {
    $intNewGroup=2
}
else {
    $intNewGroup=$nodesGroups.count+1
}

#Here should be the code for the group,properties,items line creation. Partially

$newline=$xml.CreateElement("items")

#Here should be the code for the <name>. Not ready yet

> $xml = [XML]"<Man>...</Man>"
 > $newGrp = $xml.CreateElement("group")
 > $newGrp.InnerText = "group 3"
 > $xml.Man.file.group.AppendChild($newGrp)