remove duplicates in a list

[Grant Thiessen bookitinc]

I have long used the $removeduplicates command to remove duplicates from a single list, but now I need to do more than that.

I have two lists, each of which contains 10,000 plus lines.  I need to compare them, and eliminate all the duplicated lines, to arrive at a new list with only the unique elements (of which I know I am looking for about 300 lines).

Has anyone done this? or have an idea about a simple way to do this?

Grant