Passing variables to bug tracking system

[bvorberg]

Dear Testlink team,
I'm looking for an (configuration) option to pass information to the connected bugtracking system (in my case redmine). For example I would like to add the ID of the testcase to the issue (in a custom field)
I tested out things like (kind of pseudocode) this in the bug tracker config:
<!-- Template redminerestInterface -->
<issuetracker>
<apikey>mykey</apikey>
<uribase>http://somehost.com/redmine/</uribase>
<projectidentifier>project name</projectidentifier>
<custom_fields type="array"> -->
<custom_field id="1" name="Test-ID">
<value>$TESTLINK_TESTCASE_ID</value> -->
</custom_field>
</custom_fields>
</issuetracker>

but it just writes the string "$TESTLINK_TESTCASE_ID" into the field instead of evaluating it.
Did i miss something to make it work, or is this not possible?
Thanks (also for the great work you do with the product) and regards - Boris