The Abacus program by default lists all events in order of Priority first and then by the order of entry. When Abacus sorts the events in the priority column it does it in an alphanumeric fashion. When you set the priority it will first sort things from 0-9 and then A-Z. However if your priorities have more than a single digit the program sorts by the first digit first and then the second digit.
An example of numeric sorting:
If you want to use multiple digits always remember to use a leading zero (0). Then it will sort in the correct order.
So with this knowledge you should be able to set a different priority for each event, have it show in that order and then by order of entry within the given priority level.