[Zope] Insert a variable problems

In the code below I'm trying to inserta variable for variableHere The variable name is "order". I've tried ${order} and all sorts of combos, but nothing seems to work. <tr tal:define="sort_on python:(('title_or_id', 'nocase', 'asc'), ('bobobase_modification_time', 'cmp', 'variableHere'));>