Adjust formula to ignore duplicates

[dasseya1]

The following formula works fine; but it takes into consideration the duplicates. How can I change it to count any repeat numbers only once?

=COUNTIFS(Assignment_3000_38,">"&0, plant_3000_38,"="&C220,posting_date_3000_38,">="&'Months & Dates'!$C$7,posting_date_3000_38,"<="&'Months & Dates'!$D$7)

Thanks

[FDibbins]

add a helper column and use =countif()=1 to ID the dups, and then include that helper in the countifS() using TRUE as the criteria

[Tony Valko]

Can you post some sample data and tell us what result you expect?