[Seaside] is dynamic href possible?

[Rob Whitfield]

I'd like to do something like:

<a href="resource/[fileName]">click here</a>

where fileName equals something like 'tmpName0003.pdf'

The goal is to be able to allow  a user to view a file that results from 
some processing done by my seaside application.  The file name isn't known 
until execution time.

When I try the above it seems that seaside is not performing the 
substitution, possibly because it disallows substitution inside the tag 
(just guessing). When I hover over the link I see that the URL literally 
contains  [fileName] instead of tmpName0003.pdf

What is the correct way to generate links dynamically?