I found sufficient documentation in the labs..The regular documentation (chm) should either be completed or at least say "See the labs for details on how to create a custom validator". I spent way too much time trying to track down
Additionally, the VB documentation is incorrect in at least one spot regarding the default constructor required for classes that inherit from ValueValidator.
Pg 58 of the VB Validation Lab Instructions shows an incorrect default constructor. The default constructor of ValidatorData based classes needs to set its Type property. Ex.
Public Sub New()
Without this, the configuration editor will save with a blank type attribute and then when you run you will get an argument null exception from Activator.