Although I think I personally would go about this problem the way Peg is suggesting, if you really want to use an ENVI routine you could probably use MATH_DOIT to execute a band math expression for you. I'm not 100% sure I understand the logic you're using when you write (0<100)data but i'm assuming you want pixels in the output file set to 1 if pixels in the input file are between 0 and 100, and set output pixels to 0 for all other input pixel values. This kind of expression will do that for you: (b1 gt 0) AND (b1 lt 100) Jeff