Obtain depth to create relative path

Using eXist database as data repository, including built in xpath and
xquery functions.

My current xquery search needs to determine the depth of the returned
node ($x) in the document - from the root.
I would then like to use this to generate the relative path that is
needed to access a node higher up the structure ($x will always be
deeper in the document).

So for example if the depth was 10, and the specific item I wished to
retrieve was at level 5, then I would want to create the relative
path: $x/../../../../../ps:specific-nodename
 i.e. ( (10-5) x "/.." ) + /ps:specific-nodename       (probably
done within a loop)

Below is what I have so far, but don't know how to get position or
counter to function on $x.

Can this be done without xsl? how can the relative path value be created?
TIA

- - - - - -
declare namespace ps="http://www.pasoa.org/schemas/version025/PStruct.xsd";
declare namespace wsa=" http://schemas.xmlsoap.org/ws/2004/03/addressing";
declare namespace ex="http://www.example.com";
declare namespace ph=" http://www.pasoa.org/schemas/version025/PHeader.xsd";
declare namespace pq="
http://www.pasoa.org/schemas/version025/pquery/ProvenanceQuery.xsd ";
declare namespace xsl=" http://www.w3.org/Style/XSL/ ";
declare namespace fc="http://www.w3.org/2005/02/xpath-functions ";

for $x at $i in
/ps:pstruct/ps:interactionRecord/ps:interactionKey/ps:messageSink[wsa:Address="http://www.example.com/actors/store"]/../../ps:sender/ps:interactionPAssertion/ps:content/ex:envelope/ex:store
[ex:location="/home/sj/data/file1"]/../../ex:envelope/ex:store/ex:data

let $pos := fn:position()                      <!-- this is not working ->
let $count := count(ancestor::*)+1      <!-- this is not working ->

let $view := $x/../../../../..                   <!-- this is what the
depth is to be used to set ->
return
<resultPQ counter="{$i}">
 <testcount>{$pos} and {$count}</testcount>
 <qdhdata>{$x}</qdhdata>
 <qdhkey>{$view/../ps:interactionKey}</qdhkey>
 <qdhviewtype>{$view/name()}</qdhviewtype>
 <qdhsender>{$view/../ps:sender}</qdhsender>
 <qdhreceiver>{$view/../ps:receiver}</qdhreceiver>
</resultPQ>