Zennoposter: comparing two text files

i've been using zennoposter for awhile now but for some reason i really can't put together an efficient way of comparing two text files to each other and taking out the duplicates in one of the text files. i've got one method down but it takes way to long with long lists, after i compare the two files i'm left with a list full of spaces that i then have filter of any empty spaces.

I know there has to be an easier way and if you know one i'd love to hear it. thanks.

1. loop through text1.txt getting the line 0 from text1.txt with remove option until text1.txt exists
2. regexp match what you got from step 1 with text2.txt
3. if the result is longer than 0 then write out the line to a unique-in-text1.txt

Is this what you are doing?
Anyway, I have not tried, but theoretically you could use Javascript to do this, I guess