How to prevent a user/role from accessing a version

Hi,

I'm just wondering how I can prevent a role / user from accessing a single version of a report.

We have a report that has 37 versions and 'all versions' (the parent report) have been secured to multiple roles in Appliction Security. Can I unsecure (block) just one version of the report from being accessed or do I need to remove the parent report (all versions) from each role and then secure each individual version, except for the report that needs to be blocked, to each role.

Thanks,

Tony