Here you'll find some tricks about Excel.
= Some smart formulas=
== Find case with a character (or a series)==
Let's assume you have a column filled with e-mail addresses and other pieces of information.
You want to sort only the e-mail addresses.
The function FIND return a #VALUE error
> =IF(FIND("@";A1)<>"#VALUE";A1;"")
So using IFERROR we can retrieve only the case with @
> =IFERROR(IF(FIND("@";A1);A1;"");"")
== you have two lists , you want to eliminate "doublon" ==
=IF( COUNTIFS( $C$1:$C$28;A1)> 0; "";A1)
list of "already done" Column C , fom 1 to 28.
list of "all" , Colum A
use COUNTIFS, if > 0 , exist in the lsit "already done" !