More efective sumproduct

[danovkos]

Hi all
pls. can you help me with this formula?
I wrote this question to other forum but there nobody helps me.

(http://www.excelforum.com/excel-worksheet-functions/673254-return-uniqe-from-column-b-based-column-a.html)http://www.excelforum.com/excel-worksheet-functions/673254-return-uniqe-from-column-b-based-column-a.html

I have this formula:


=IF(SUMPRODUCT(--($B$4:B4&$M$4:M4=B4&M4))=1;M4;"")

If i use this formula it takes a lot of time by my huge data (6000 rows).
BUT If are my data sorted, than i know, that i have all the same ID numbers together (column B), is it possible modified this code, that it doesnt counts/watch whole column but only cells where in column B is the same number? Of course this number starts only ones in column because it is sorted.

I hope it will works quicker.

Please anyone knows how do this?
thank you

[Bob Phillips]

In a helper column, E say, add a formula of


=B4&M4

and then use


=IF(COUNTIF($E$4:E4,E4)=1,M4,"")

[danovkos]

yes, this is good.
thanke you