Now EXCLUDE contacts associated with all Accounts with this custom module called: "Medical Billing" 

with the drop down selection = Yes

So: Take this mailing list and exclude emailing contacts who already have this Medical Billing service. 

Is this possible? i don't want to have to go into each contact and add if they are a medical billing client or not. for me it is much easier to add if they are a medical billing client to the the account rather than each individual contact.

i want to send a marketing email but don't want to send to the client if they already have the service :P 

any comments would be great!