Selecting Values in XPath depending on values at same level

I've got this partial XML

 <Events>
   <Properties>
     <Property Descriptor="1">VALUE1</Property>
     <Property Descriptor="2">FOO</Property>
     <Property Descriptor="3">BAR</Property>
     </Properties>
   <Properties>
     <Property Descriptor="1">VALUE2</Property>
     <Property Descriptor="2">NO</Property>
     <Property Descriptor="3">NOTHINGHERE</Property>
   </Properties>
 </Events>

Hi can I query the first occurrence of Property Descriptor="3" when Property Descriptor="2" = "FOO"? Result here should be BAR

I tried //Properties/Property[@Descriptor="3"][..//Property[@Descriptor="2"] = "FOO"] but it's now working.