counting values only once
 

I have a problem and was wondering if there was a way to solve it that I
havent thought of. I have a column that represents months. It stores then in
numeric format, i.e. 1 for January, 2 for February etc€¦ The next column is a
reference to a machine, in the format 001/0019 or 005/0041 and so on.
Now one machine can come up in the same month more that once. I want a pivot
table that shows me the total number of machines in each month, but not count
the same machine more that once in any month.
I managed this by sorting the two columns first by month then by machine. I
then added a third column with the following formula
=IF(AND(E2=E3,D2=D3),0,1) so that the month and machine values are compared
to the next ones.
This works, but the person requesting a solution says he doesnt want the
columns sorted. Is there a way to do this without sorting the columns?