Filter email using X-SPAM-LEVEL

[section1]

Hi all!
I'm trying to filter an email depending what the antispam report in the header 'X-SPAM-LEVEL'
It's that possible ? because i tested adding a rule with field X-SPAM-LEVEL=Spam and
for some reason isn't getting hit by the rule.. If i change that field to something like
Subject=Test the rule is working...
Looks like when filters rules are "scanning" the email that header doesn't exist.

I have a rule at the to(priority 99) that has 'Modify Spam Level' action to all emails.
Can be a good type of filter because yo can customize spamassassin rules
and then at Filter level do things depending what SA add to the score result.
Any ideas ?

thanks