To put it in a policy quarantine, probably something like this:
check_Vinays_header:
if (header('X-Vinays_header') == 'nice guy')
{
quarantine ('Policy');
}
If you want to put it in the SPAM quarantine, where users can release it, use this as the action instead:
check_Vinays_header:
if (header('X-Vinays_header') == 'nice guy')
{
insert-header('X-Ironport-Quarantine');
}