How do we know which error is generated?

I know that there are 3 kinds of errors...1. Generated by QTP 2. Generated by Script and 3. Genetated by AUT. How do we know which error is generated by QTP or Script or AUT?

NOTE : [I][This question was asked by Joelu][/I]

'error handling for vbscript errors
on error resume next

if err.number <> 0 then
msgbox err.description, vbokonly, err.number
err.clear
end if
'error handling for qtp internal errors
if getlasterror <> 0 then
msgbox(describeresult(getlasterror))
end if

for application errors you have to use the api of your aut. But this is not everywhere available/possible

Regards,
Nawab