NACL: how to include a specific user group only when a certain conditions is met

Good afternoon,

We have a document class, subject to a workflow, that has different permissions in different workflow states.

For each of the workflow states, there is a Named Access Control List (NACL).

Now, when a specific condition is met, another user group that is not part of the workflow should have the permissions to view the document for the remaining steps in the workflow.

I can't include this user group in the NACL's by default, because this group should not allowed to see documents where the specified condition is not met.

Is there some way to be able to include this user group in NACL's when the the condition is met?

I want to keep the permissions automatically set so "disable automatic permissions" is not an option.

Thanks!

Patrick.