Lets say I have a custom header called <ArtifactSubject and this is defined
in the right section. Can I link this to a custom property or some other
document content (Source) so that when the custom property changes or
whatever it is linked too this would change the content of the
<ArtifactSubject defined in the custom header. Similar to the way Word does
with its custom properties that are assigned to Fields that can be defined in
a header.

If this cannot be done, I assume the only way I can do it is by manipulating
the PageSetup.RightHeader text assuming I want to use a macro driven function
that would gather the value for the <ArtifactSubject from some form and
update the header text with it.