Deb G wrote:
I import data from a different application into a .csv file, then save it as
an Excel workbook base.xls, using Excel 2000; that data is in correct sorted
order, column A runs from 00-00000 to 99-99999; there are about 230 items in
that series. Another workbook, calcu.xls uses the LOOKUP function to extract
data from the first workbook. Everything worked fine until we added 6 new
items in base.xls. Now those last six item Lookups in calcu.xls return a
blank space (not an error) instead of the actual item. When I use the Sort
menu to sort base.xls, the problem goes away, even though the actual sequence
of the data remains unchanged. If I change the formulas to VLOOKUP, they can
find the data in the original base.xls file. I'd like to avoid changing all
my LOOKUPs to VLOOKUPs, it would take quite awhile.

When you invoke a lookup formula with LOOKUP, the "lookup table" must ne
set in ascending order on its match-range (that is, on its leftmost
column) and maintained in ascending order when new records added to it.
BTW, could you post the LOOKUP formula that you're using?