The inverse of Interset

[Jim Hurley]

The intersect command (intersect arrayOne with arrayTwo) removes the elements from arrayOne that not in arrayTwo.

What I need is an array of the elements removed. Intersect leaves everything but.

Is there an array operation that accomplishes this? 
The dimensions of my arrays are very large and so using "is among" on the keys is not an option.

Jim Hurley