Unfortunately, there is not currently a way to do this - it is what I was alluding to in my previous post.
I am interested in implementing this feature, but would like to solicit some input as to how existing users on existing followups should act.
It seems simple, really:
1) Users on a followup BEFORE the one added proceed as normal, receiving the new followup in turn.
2) Users on a followup AFTER the one added proceed as normal and never receive the new message.
I don't know why I didn't implement this before. :-)
The only problem now is the followup sequence #. These should probably be "re-arranged" each time you add a new followup. That, or the numbers "1", "2", "3", etc could become cosmetic, storing the actual "order" of followups in a new table. With a change like this users' Seq #s would not necessarily increase in order.
What about a feature to move followups up and down in sequence? I couldn't recommend you do this on live lists... The only way I can see to avoid problems with moving messages around is by storing the messages received for each user and skipping already sent messages.. I am hesitant to track this data as it will take up a lot of extra database space. Therefore, I should probably just stick to providing features to add and remove followups in sequence.
I'll make a note of this and should have the feature in a near future update.
Regards