[Zope] Calling dynamic zsql method from zpt?

I've searched everywhere for a seamingly obvious thing to have in the documentation - how to call a dynamic zsql method from a zope page template using arguments. What I need is something like this: <div tal:define="sqlRows nocall:here/ZSQLTerritoryList(parent_id=parent_id)"> <select name="country_list"> <option value="">ANY</option> <option tal:repeat="sqlRow sqlRows" ... etc... but obviously the first line of code doesn't work. How else are variables passed do zsql methods from page templates? Thanks, Nick