Set XML attribute from SetValue using Xpath

Question

Is there a trick to assigning a value to an attribute of an element in an XML variable using XPATH inside a setValue activity?  When I try something like
Location
/process_var/xml_var/test/@ID
Expression:
/process_var/test_value
it complains about the @ sign in the location assignment.  I seem to be able to retrieve attributes just fine.

Answer 1

Still having this issue.
If I have an XML process variable which currently contains
<Document>
    <Title />
    <Author />
    <Date />
</Document>
Try this, it fails.
Location: /process_data/xml/Document/@ID
Expression: 54
Try this, it works.
Location: /process_data/xml/Document/ID
Expression: 54
Now, alter the XML by adding an ID attribute
<Document ID="">
    <Title />
    <Author />
    <Date />
</Document>
Try this, it works, where it failed earlier.
Location: /process_data/xml/Document/@ID
Expression: 54
It appears to me, you can ADD a new node, but you can't ADD an attribute