Hi Charles,
As per my understanding you want to differentiate manual input versus auto detection from a device like bar code reader
In general bar code reader SAP Screen will be in small size and there will be a different transactions to accommodate the handheld terminal/device i.e., LM01.
So there fore transaction code itself will be different, so you can identify easily, but if you are using the same transaction for manual input versus scanner input I don't think you can differentiate.
R,
Amala