interceptor and converter cycle

["Shannon, Andrew" <an...@pqa.com>]

We have a pojo with a birthDate property whose setter is going to parse
the String value and throw an exception if it cannot be parsed.
 
We are not using a date picker, the value must be typed in as a String.
 
The ParametersInterceptor always picks up the Exception even though I've
tried implementing a converter.
 
I've read several posts on converters, but none seem to have the same
kind of model implemented that we do where the incoming value is
enforced by the setter in the pojo.  I'm not sure when the framework is
trying to set the posted value and how I can get in front of it with the
converter.  I'd prefer not to have to put an interceptor in just for
this, but would if there was a good case for it.
 
Is anyone else using the pattern?  What else might I try?
 
BTW - I just started using S2 and I'm totally psyched about it after
using Tapestry for the last 2 years.  S2 seems mostly easy to learn (it
lives up to the hype, at least in my opinion) but I'm totally stumped on
this one.
 
Thanks,
Andrew