You could certainly try this using Remote Mode. However, the toxins which make us sick are chemicals produced by moulds, and these have no DNA - only the mold itself and its spores can have DNA. In the absence of a DNA specimen, the only way to get at mould behind a wall is either to tear it down, or use a Spooky Central in plasma mode - this will penetrate the entire fabric of your home. Please check the attachment-the SC mold presets.
We have a specific protocol for this: http://www.spooky2-mall.com/blog/pests-and-mold-protocols-for-spooky2-home-care-kit/ This has been proven to be very effective by a lot of users.