Hi everybody!
I'm trying to figure out how I can set the "order" attribute of the tree tag with the value of a variable:
For example:

<dtml-unless treeOrder>

<dtml-call "REQUEST.set('treeOrder','title')">
</dtml-unless>

<dtml-tree sort=treeOrder>
<a href="&dtml-absolute_url;" target="previewPanel"><dtml-var title></a>
</dtml-tree>

By doing this, I get the following error:

Error Type: AttributeError
Error Value: treeOrder

Same thing happens whenever I try with:

sort=&dtml-treeOrder;

sort="&dtml-treeOrder;"

Currently I am using this solution, which works, but it isn't clean:

<dtml-unless treeOrder>
      <dtml-call "REQUEST.set('treeOrder','title')">
</dtml-unless>
<dtml-if expr="treeOrder=='title'">
    <dtml-tree sort="title">
      <a href="&dtml-absolute_url;" target="previewPanel"><dtml-var title></a>
    </dtml-tree>
<dtml-elif expr="treeOrder=='id'">
    <dtml-tree sort="id">
      <a href="&dtml-absolute_url;" target="previewPanel"><dtml-var title></a>
    </dtml-tree>

<dtml-elif expr="treeOrder=='user'">
    <dtml-tree sort="user">
      <a href="&dtml-absolute_url;" target="previewPanel"><dtml-var title></a>
    </dtml-tree>

<dtml-elif expr="treeOrder=='date'">
    <dtml-tree sort="date">
      <a href="&dtml-absolute_url;" target="previewPanel"><dtml-var title></a>
    </dtml-tree>
</dtml-if>

Does somebody knows how to render this variable?

Thanks in advanced,

Josef.