There are several ways to simulate shattering glass. It all depends on the degree of realism you are looking for. I will explain one method which is easy to do and looks still good:

• create your table (or window) as two seperate entities: the table itself and the glass plate as seperate model. Arrange them in WED so that they fit together.
• Take the glassplate and save it as seperate file. Cut the glass plate into pieces, but keep them together (just slice the polygons)
• there is a explosion plugin in Milkshape, which can shatter polygons away. Load the slice glas plate into Milkshape (or any other modeler which supports such a feature) and play with the values (explosion point, flying direction, speed, rotation, etc.). The plugin will create an animation for you. The more frames you will use, it will look smoother and more realistic
• save the animated file as MDL file
• when it comes the time to shatter glass, morph the glassplate into the sliced and animated glassplate
• play the animation and start other effects. Maybe you can add/spawn glass shatters under the table
• make the animated plate passable so that the boxes can pass through the table (make the table polygoncollision enabled)
• you can script the box physics, use newton or the A6 physics engine or fully script the box behaviour (prescripted)

I hope this gets you started

Ciao - Christian