Setting the value of an XML node among nodes with the same name

[nbrege]

Suppose I have the following XML string:

                                       <PartOverrides>
                                           <PartOverride>
                                               <Name>Cab.Case.LF</Name>
                                               <Parameter>
                                                   <Name>BAND</Name>
                                                   <Type>T</Type>
                                                   <Value>NEE</Value></Parameter></PartOverride>
                                           <PartOverride>
                                               <Name>Cab.Case.RF</Name>
                                               <Parameter>
                                                   <Name>BAND</Name>
                                                   <Type>T</Type>
                                                   <Value>NNEE</Value></Parameter></PartOverride>
                                           <PartOverride>
                                               <Name>Cab.Interior.PT</Name>
                                               <Thickness>19.000</Thickness>
                                               <Material>R000300</Material></PartOverride>
                                           <PartOverride>
                                               <Name>Cab.Interior.PT@2</Name>
                                               <Thickness>19.000</Thickness>
                                               <Material>R000300</Material></PartOverride>
                                           <PartOverride>
                                               <Name>Cab.Face.DWR_OPEN.DBOX.DWR.S_DSLAB</Name>
                                               <Shape><template firstid="1" unit="mm"><geometry><entity id="1" type="line2d"><end><x>604.8325</x></end><parameters><parameter name="_PROFTYPE"><value type="4">1</value></parameter></parameters></entity><entity id="2" type="line2d"><begin><x>604.8325</x></begin><end><x>604.8325</x><y>349.245</y></end><parameters><parameter name="_PROFTYPE"><value type="4">1</value></parameter></parameters></entity><entity id="3" type="line2d"><begin><y>349.245</y></begin><parameters><parameter name="_PROFTYPE"><value type="4">1</value></parameter></parameters></entity><entity id="4" type="line2d"><begin><x>604.8325</x><y>349.245</y></begin><end><y>349.245</y></end><parameters><parameter name="_PROFTYPE"><value type="4">1</value></parameter></parameters></entity></geometry></template></Shape></PartOverride>
                                           <PartOverride>
                                               <Name>[email protected]_DSLAB</Name>
                                               <Shape><template firstid="1" unit="mm"><geometry><entity id="1" type="line2d"><end><x>604.8325</x></end><parameters><parameter name="_PROFTYPE"><value type="4">1</value></parameter></parameters></entity><entity id="2" type="line2d"><begin><x>604.8325</x></begin><end><x>604.8325</x><y>349.245</y></end><parameters><parameter name="_PROFTYPE"><value type="4">1</value></parameter></parameters></entity><entity id="3" type="line2d"><begin><y>349.245</y></begin><parameters><parameter name="_PROFTYPE"><value type="4">1</value></parameter></parameters></entity><entity id="4" type="line2d"><begin><x>604.8325</x><y>349.245</y></begin><end><y>349.245</y></end><parameters><parameter name="_PROFTYPE"><value type="4">1</value></parameter></parameters></entity></geometry></template></Shape></PartOverride>
                                       </PartOverrides>

How would I set the value of the <Material> node under the 3rd <PartOverride> node? (Highlighted above)
The string above is part of a larger XML string that is defined as an XElement. The kicker is that the 3rd <PartOverride> node may not always be 3rd, so I think you would have to get the node based on the value in the <Name> node...