Is it possible to use a Multimeter for detecting electric leads?
You won't be able to reliably detect any current flow through the drywall/sheeting on your wall without using some active components. One of the comments suggested a metal detector which is basically what you're creating with some wire loops, a transistor and a power supply. Check out this $10 diy metal detector kit to get the basic idea:
Elenco Soldering Metal Detector Kit
There are cheap passive non-contact detectors that'll work if you hold them up right in front of an active power outlet but that wouldn't work through a wall.