Damage macro that properly reduces damage from damage reduction

I'm looking to create something that can handle a large number of damage dice, while properly reducing the damage for 5e's Heavy Armour Master, which reduces damage of physical weapons by 3, minimum 0. An example attack would be 50d6, where each d6 is an individual attack for the purposes of damage reduction.  The operation I'd like to use would be rolling 50 individual d6-3, but with a minimum of 0 for each d6-3.  Obviously I could use a d4-1 and get a similar range of results 0-3, but it affects the weighting and I want the player's feat to feel useful (50% chance of 0 damage.)  Dropping negatives could probably work as well if that's possible, while reroll obviously ruins the weighting as well.

You can tell it to roll 50d6-3 and tell you how many of them came back as 1 or greater [[{50d6-3}>1]], but that doesn't tell you what each individual result is after taking off the 3

That's perfect to adapt a solution, thanks.  I can roll ([[{50d6-3}>1]]d3) to simulate the damage, using the number of results above 0 as my number of d3s.

Glad you could make it work.