[exim] Accessing Bcc headers within acl_check_data section

Hello,

I have to filter email based upon a number of conditions 9such as: for
given source (From/Reply-To) email domain prevent sending messages to
another email domain.

The rules are being handled by a script I call in 'deny condition'
statement in acl_check_data section. It checks for correct data in
To/C//Reply-To/From combination and denies sending with custom message
when conditions are not met.

The problem is I can't pass Bcc headers to the script. Is it possible to
access Bcc headers (via $header_bcc:) in ACL section(s)?

Thanks.

Sincerely,
Konstantin