The Endpoint Repository is not part of the Event Service, and you cannot add it.
As a workaround what might work is to add in the event service an attribute like 'increasecounter=true', then if you do a CoA, in the 802.1X service (or MACAuth, etc), you can check if that attribute is set, in which case you clear the increasecounter attribute and set the increased Counter value to the Counter attribute.
If you think you have a proper use case for this, please contact your local Aruba (ClearPass) SE to bring this to the attention of our product management. For me, it is the first time I see it, and as you see with some workarounds you can build it; if it is useful for the broader audience, having this as an official feature may make sense.