use a helper worksheet

starting in cell A1, number from 1000 through 2000.
starting in b1, use a formula =COUNTIF('good data'!$A$1:$A$2000,'helper
sheet'!A1)
copy formula from B1:B1000

now do an autofilter on column B. Filter for value of 0.

"andy" wrote:

I've just been asked if there's a way Excel can easily find if there are
missing numbers from a sequence of numbers in a column.

For example, the column contains numbers between 1000 and 2000, but the user
isn't sure if every number between 1000 and 2000 is present in the column,
to possibly make it more interesting, each number may appear more than once
in the column.

Any ideas?

Cheers,

Andy