OK, I've PM'ed you with the script. (Not that it's secret, but there is some reformatting going on, both with AFNI and TORTOISE for making calculations of tensor things more direct-- more to follow on the MB about this.) It also describes using a whole brain tracking run to visually check things, for sanity purposes.
I've assumed you have a constant nonzero diffusion weighting factor (i.e., a single bvalue = 1000 s/mm2 or something). If not, let me know, because then you'll need a different version (dealing with this elegantly is one of the formatting changes a-comin').
--pt