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I'm not sure it's *that* critical.... wouldn't it still bring back correct answers however your data is sorted, although I have to admit that it would affect performance speed if your vlookup values are right at the bottom of a list of a few thousand entries

That depends if you're using TRUE or FALSE in the formula Chris.... tho in this eg you're probably right...

from the Help on VLOOKUP....

VLOOKUP(lookup_value,table_array,col_index_num,range_lookup)

If range_lookup is TRUE, the values in the first column of table_array must be placed in ascending order: ..., -2, -1, 0, 1, 2, ..., A-Z, FALSE, TRUE; otherwise VLOOKUP may not give the correct value.

If range_lookup is FALSE, table_array does not need to be sorted.

If VLOOKUP can't find lookup_value, and range_lookup is TRUE, it uses the largest value that is less than or equal to lookup_value.