The metal sleeving may work as shielding, as long as you somehow made provisions to ground the sleeving (which is the key to proper shielding.)
You could also look more into this product:
http://www.acsindustries.com/product...e/default.html
Or best (and easiest) option: Get yourself some shielded 3 wire Belden Cable from your local or nearest electrical wholesaler (or online). Then you don't have to wrap anything.