I have a spreadsheet that is 6 columns by 58000 rows. In this spreadsheet I filter data. However I want to count the number of unique entries in a list (that are not the same). See example:

ORDER RDATE RTIME PHL SQA# FDATE
XHGB 8/18/08 5:00 JW F15031 8/18/08
XWBC 8/18/08 5:05 JW F15031 8/18/08
XHCT 8/19/08 7:05 LW S15033 8/19/08
XALT 8/20/08 11:24 FS W13055 8/20/08

I am counting the number of unique entries by the SQA# field (which should be 3). What is the best way to pull this data for 58000 entries if sorting by the SQA#? Thanks