Signal question

[nenelan]

One way that could work is as follows.
You could have the three correct ones pass a 1 as their signalwith to the event handler, have the incorrect ones pass a 4 as their signal to the event handler. Have the mob receiving signals add up the signals.
Once we hit "3", spawn the chest and depop all other mobs. If we end up going over 3 at all, completely reset the event.
That should give you an angle to how to get started, if you need anything else, post what you tried from using these suggestions and we'll help further!

EDIT: DOH! I read that wrong. You said specific order. Above would not work for that. Leaving it up for posterity though as it would work if a certain amount of mobs being killed.

For a specific order, the first mob could pass a "1", the second mob could pass a "2", and the third mob could pass a "3", with "0s" being passed by the incorrect mobs. Again have a counter variable that would start at 0. Test the signal being sent. If it is 0, reset the event. Then, if it does not reset, test the variable against the signal, if it was incremented by 1, we would consider that a correct kill, and store the signal as the variable. If it was incremented by anything but 1, reset the event. If 3 ever gets stored, spawn the chest. For example:
We start with a 0. We kill the wrong mob, a 0 gets passed and we reset the event.
We kill mob with signal 2, the variable test 0 vs 2, and it did NOT increment by 1, so we would reset the event.
We kill mob with signal 1, the variable would be tested 0 vs 1, and it did increment by 1. We replace the variable with the 1.
Next we kill mob 2, the variable would be tested 1 vs 2, and it did increment by 1. We would replace the variable with the 2.
Next we kill mob 3, the variable would be tested 2 vs 3, and it did increment by 1. We would replace the variable with the 3, and since that is what we were looking for for a successful win, we would end the event and pop a chest.
If, for instance, we killed mob 3 after mob 1, the variable would be tested 1 vs 3, and it would reset the event.

Hopefully that helps for the general gist of how it would work and you should be able to work from there. There might be easier ways to do this, but this is the first one that came to mind for me.