My recommendation would be to experiment with negative values in this scenario:
div { width: 300px; height: 300px;
/* Give this a try. */
box-shadow: inset 4px -4px 7px -4px #000;
}
The first 4px adjustment moves the shadow box to the left by 4px, concealing what would typically appear on the right side if kept at 0.
The second -4px value shifts the shadow downwards vertically, effectively hiding the top part of the shadow.
While the 7px blur value may seem excessive, adding a spread of -4px will clip that extra blur, resulting in a soft grey shadow edge rather than the usual harsh black one.
Take a look at my demonstration here:
http://jsfiddle.net/khalifah/vVUB5/