Mahmood said:
"Your on error event you get the Count which tells you the byte that had parity error"

Here is what it says in the online help about the TCustomComPort.OnError Event:

Occurs on line status error.

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TComErrorEvent = procedure(Sender: TObject; Errors: TComErrors) of object;
property OnError: TComErrorEvent;

Description
Write OnError event handler to take specific action when a line status error occurs. Line status errors are ceFrame, ceOverrun, ceRxParity.

Note
If application calls LastErrors method inside OnError event, it returns empty result set. Use Errors paramater instead.

The AsyncPro OnTriggerLineError is similar.

I don't see anything about a Count - where did you read that?