KACE Product Support

I have been looking all over for some SQL that could calculate the true 'Age' of a ticket - meaning how many days/hours/minutes it has been sitting open, taking into account nights and weekends. 

I know KACE is able to calculate this in theory, because the Service Level Agreement settings allow you to use the defined business hours.  However, I don't know *how* it does that and I'd like to be able to use business hours in custom rules.