Elfa:
Enter this formula in column C:
=IF(ISERROR(VLOOKUP(B1,$A$1:$A$10,1,FALSE)),"No","Yes")
If this formula is in cell C1 then it will return 'Yes' if the value in cell B1 is anywhere in the list contained in column A. If you want to search all of column A and not just cells 1 through 10...