TreeTagPatch

  This is a "hotfix" product. Hotfix products can be installed to incorporate
  modifications to Zope at runtime without requiring an immediate installation
  upgrade. Hotfix products are installed just as you would install any other Zope
  product.

  The current tree tag accepts an attribute urlparam (a string constant).
  This attribute defines a query string which is included in the expanding
  and contracting widget links. Unfortunately, it only accepts constants, not
  variables or expressions.

  This hotfix patches the <dtml-tree> tag to make it accept a new attribute
  "urlparam_expr". When the tree is rendered, this parameter will be evaluated
  (if present) and the result will be appended to the expanding
  and contracting widget links. With this feature you can now pass on
  _dynamic_ query string parameters:

  <dtml-call "REQUEST.set('myParameter', '5')">

  <dtml-tree ... urlparam_expr="'example='+myParameter">
  ...
  </dtml-tree>

  Note:
  You cannot use urlparam and urlparam_expr at the same time.

  16-Apr-2001 by Danny W. Adair