vezerid, I can't get your formula to work properly. Should it be applied to a
number already with a check digit in it? It didn't work on the following
number in the example from the link you gave me

516192872

The check digit should be 2 so the total number is 5161928722 but when I ran
your formula on the above number, the check digit it came up with was 10
which indicates an error.

The formula you gave me was:


=11-MOD(SUMPRODUCT(VALUE(MID(A1,ROW(INDIRECT("1:"&LEN( A1))),1)),
MOD(ROW(INDIRECT("1:"&LEN(A1)))-1,6)+2),11)

To append the check digit to the number

=value(A1&_formula_)

Michelle