There is already a Sandbox Feature in the free version but the program controls what should be run sandboxed.
In the free version, that's as much of that feature that's available to us. Just as with some of the other features,
you have 2 choices, either pay for the Pro or Internet Suite or, find another third party program to fill that void.
avast! free is great but, it is lacking some of the great add-ons built into the paid versions.