adding custom fields in the batch interface

I have built a batch extension that has a few custom fields. It appears to work fine, if I have added the custom fields into the template.

However, if the template does not have the custom fields, and I add them on the fly, using the "customize fields" option within the batch itself, when I am creating the batch, it does not seem to activate any of the batch extension stored procs, with the result being that I can enter data into the custom fields, but the data disappears once I save or validate.

Has anyone else experienced this or found a way around it?

Thanks.