sorry first post had bad formatting

Thankyou for everyone's help yesterday it was great. I have one last
thing that is bafaling me to do with the same thing.

I have a column in D that shows the number of days an invoice is over
due


| A | B | C | D |
10 N/A yes 0
10 N/A yes 0
11 N/A no 2
11 N/A no 2
12 N/A yes 0
13 N/A no 1
13 N/A no 1
13 N/A no 1


I wish to sum the number in coulmn D for those that are overdue (no
in
Column C) and that are unique entries (column A, invoice number), in
this example there are 4 unique entries.


With the help from everyone yestarday i have manged to be able to sum
up the number of invoices that were overdue (Column C=no), so in the
obove example the result would be 2 (invoice 11 and 13) by useing
this
array formula.


=SUM(N(FREQUENCY(IF(C:C="No",MATCH(A:A&"",A:A&"",0 )),MATCH
(A:A&"",A:A&"",0))0))


I am at a loss at how i can then extend this to sum up the same
corrospnding values in column D.


Oh and i then need to also devide this by the total number of
invoices
that failed.


Hope someone can help.


Many Thanks
Gareth