So confused about error checking

For about a year on and off I have been trying to get a global error checking procedure to work. This week I attacked it with a vengeance only to be knocked down again.

In the Global Init of my app I have:

GLOBAL

//General error processing
WHEN EXCEPTION
ErrorHandling()
END

ErrorHandling() is a procedure that sends out an email but it is never called.

My latest test while debugging I get:

ErrorInfo = Duplicates found for <GUID> key on <Contact> file.

The Exception code is not called. Why not? What on earth am I doing wrong.

BTW this is an AWP site if that makes any difference.

Many thanks in advance.