A timing belt usually makes a loud squealing noise (like a 'shriek/scream') when it is worn or slipping, not a grinding noise.
A quick check - before you start the car - is to pour some water onto the inside of the belt where it goes around the pulleys. If there's no noise at start up, you know it is the belt at fault (or the metal pulley/s are worn).
There are kits to replace the timing belt (and bearings). Have a look on Ebay:
843results for accord v6 timing belt
If the noise happens before the car moves - it obviously can't be your brakes. When backing up the noise may appear louder simply because your head is turned ..
If the noise is actually coming from a wheel, it possibly could be the backing plate on the brakes - the thin disk behind the brake may be rubbing on the rotor.
However.. a grinding noise ... if it is coming from the front of the engine in the general area of the timing belt be very wary - if a bearing or the belt fails, your engine will be history.
Why not give a mobile mechanic a call? Those guys are usually quite good and a lot cheaper than a workshop