"OnRxChar event has Count which is the number of bytes received."

That is exactly the problem!
The OnRxChar event tells me "I've got 3 bytes", and the OnError event tells me "error(s) occurred" - but there is no way to tell which byte(s) had which error(s)! :-(

"I think in your onerror event you can check the count also."

Even if you could, it still gives the same problem. :-(

"What baud rate are you talking about?"

9600.
AsyncPro seems to give me at lease 2 or 3 bytes in each OnRxChar event - I think it waits for a gap between bytes before it raises the Event?