Macro Help for GURPS

I have created the following macro for automating damage rolls (I hate doing math during play), and it generally works perfectly fine... as long as the end result is a positive amount of damage being inflicted: /em causes [[ceil((?{Base Dice}d6 + ?{Adds} - (?{Target DR} / ?{Armor Divisor|Default, 1|Paintball (0.2), 0.2|Hollowpoint (0.5), 0.5|Armor Piercing (2), 2|Shaped Charge (10), 10})) * ?{Damage Type|Crushing (cr), 1|Cutting (cut), 1.5|Impaling (imp), 2|Small Piercing (pi-), 0.5|Piercing (pi), 1|Large Piercing (pi+), 1.5|Huge Piercing (pi++), 2|All Skull Hits, 4})]] points of damage (after armor). If, however, the target is wearing some obscene amount of armor and the wounding multiplier is more than 1, the end result is often something ridiculous like "Player causes -40 points of damage (after armor)." I am trying to figure out how to tweak the macro so that any negative number results will display "0" instead.  Any guidance?

You need to use the Keep Highest modifier, like this: /em causes [[ {ceil((?{Base Dice}d6 + ?{Adds} - (?{Target DR} / ?{Armor Divisor|Default, 1|Paintball (0.2), 0.2| Hollowpoint (0.5), 0.5|Armor Piercing (2), 2|Shaped Charge (10), 10})) * ?{Damage Type| Crushing (cr), 1|Cutting (cut), 1.5|Impaling (imp), 2|Small Piercing (pi-), 0.5| Piercing (pi), 1|Large Piercing (pi+), 1.5|Huge Piercing (pi++), 2| All Skull Hits, 4}),0d0}k1]] points of damage (after armor). (I added line breaks for clarity, you'll probably need to delete those)

I suspected that would be the answer... I just couldn't figure out how to incorporate it.  Everything I tried resulted in a no-go.  Thanks! Tested it out, and it works perfectly.

Glad to help :)