Download's method, in its simplicity, is arguably the best method here (as far as just performing the count up or count down is concerned) :P it can be useful to abstract and combine in the way sunslayer did, but oftentimes it's just not suitable and leads to less efficient and less readable code.

that said, here's another method (without any validation) that uses $timer().reps as a counter:

alias count .timercount $calc(($1 - $2) ^ 2 ^ .5 + 1) 1 say $!calc( $2 $iif($1 < $2, -) +$timer(count).reps)