Opensmppbox and filtering MT messages by sender address

Hi All,
I didn't get answer to my question in [email protected] maillist, so as the
last resort I'm posting it in [email protected].

I configured kannel 1.5.0 to allow sending of messages as follow:

ESME => opensmppbox => sqlbox => bearerbox => external SMSCs
Is there any way to block SMS from certain sender addresses anywhere in this
chain of boxes?

I know there are white-list-regex and black-list-regex in core group but it
seems that those parameters are filtering the messages going in the opposite
direction (from external SMSC to bearerbox) and I need to do filtering in
direction indicated by =>.

Best regards,
Miranda Weasley