'=B'.$line_count - 'B'.($line_count_plus_1)

##</code><code>##

'=B'.$line_count .' - B'.($line_count_plus_1)

##</code><code>##

"=B$line_count - B$line_count_plus_1"

##</code><code>##

sprintf '=B%d - B%d', $line_count, $line_count-1