Just so we're all on the same page here, a 24/2 w/shield typically has a foil shield, and a bare wire called the 'drain', which certainly can and should be used as a third conductor, as long as it is used for the 'ground'.
I've done this exact same thing on several occasions, and I even used what is basically a miniature XLR connector in a space between openings on a multi-gang wall plate behind an entertainment cabinet.
Bart's initial question's topic said "2 conductor shielded", and his question implied it when he said "the ground wire of a 24 awg 2 conductor cable", so I hereby defend the affirmative responses. So, there! : - )