What you need is the Match function:

=MATCH(A1,Sheet1!A:A,FALSE)

And if you want to ignore empty cells:

=if(A1="","",MATCH(A1,Sheet1!A:A,FALSE))

And for ignoring errors:

=IF(A1="","",IF(ISERROR(MATCH(A1,Sheet1!A:A,FALSE) ),"not
found",MATCH(A1,Sheet1!A:A,FALSE)))


hth


Carlo