Hi,

in C1 enter

=IF(SUMPRODUCT(--(B1=$A$1:$A$2000))0,"True","False")

copy formula down

"Katerinia" wrote:

COL of codes in A (full List of codes of about 2,000)
COL of codes in B (selection of COL A codes of about 850)

IF COL B code matches COLUMN A code, then true, else false