How can I define filters and actions to block all responses which is larger than 5MB?

hi there,

As the title says, how can I define such filters and actions?

Maybe the really hard part is how to describe 'larger than 5MB' using pure
regular expression.
I tried to tag out all responses larger than 5MB using a pair of filter and
server-header-tagger action, but the regular expression in the
filter definition is awkward.

Is there any better way?

Thanks in advance for any reply.

-- 
Regards.
Wen Yue