my $formula1 = $ws->store_formula('=(12*A91)+MONTH(L$39-1)-MONTH(A92)+1');   


##</code><code>##

$ws->repeat_formula($row, $col, $formula1, $fmt->{'number'},
                                     qw/^A91$/, $diff,
                                     qw/^A92$/, '$A' . $current_row
                                );