Email subject auto-populate in B1

Experts,

I have a client who wants to auto-populate the Subject line in the 'Send Message' screen when internal email function is used in B1.

The logic is that if the document attached is a Sales Order (Object 17) then the Subject should read "Company Name - Order Confirmation".

If a Invoice is attached (Object 13) then the Subject should be "Company Name - Invoice".

I looked at table OALR and could not find a field that specify which type of document is attached.

Is there another table that I can look at? Os this even possible?

You help would be greatly appreciated.

Marli