To be able to exclude contacts based on previous campaigns they've received

For example - as we're running multiple events this year, we are inviting people within a 60 mile radius of the event location. However, some of the people who attended the Huddersfield Event are still being included on the Chesford Grange campaign e-shot, as we did another 60 mile radius of Chesford Grange, and this has meant that some contacts who fall between these two locations could be invited to both. This is actually great, because it means if someone couldn't make Huddersfield, they will still be invited to Chesford. But, for those who actually attended Huddersfield, we don't want to send them EMM about Chesford. 

So, at the moment, I'm having to go through the list of contacts in the Huddersfield Attendees campaign, go to each contact record and go to their 'Campaigns' tab, scroll through the campaigns they have received from us previously and will receive in the near future, and remove them from the Chesford campaigns. Quite a manual process - not awful as these events are relatively small, in that only 20-30 attendees would attend an event (so not that many contacts to run through their campaigns and check), but still a little annoying. Would be good to eventually have it so that, as a step in the process of the wizard for targetting contacts maybe, it could have a step with something like 'don't include any contacts who are in X campaign activity (a drop down list of activities)' or something...Thanks!