Additional Dice Based on X

I'm wondering if there is a way to add dice to a damage roll based on a modifier. This is for a Warhammer 40K Deathwatch game for the Horde rules. The way the mechanic work is that the Horde does increased Damage based on it's Magnitude - think combination of numbers/willingness to fight/etc. So for example a Magnitude 30 Horde would do an additional +2d10 Damage with it's attacks. I'm assuming that if I wanted to do this all behind the scenes it would involve use of the API so instead I want to do it as a a modifier in the roll. I know I can add a numerical modifier by doing ?{Modifier|0} but that's not what I'm after. Am I missing something or is this beyond the scope of freebie level Roll20?

I'm not quite sure what you're after, but I'll note that one can put dice equations in a roll-query. It is something I do for my sneak attack dice: ?{Sneak attack?|3d6} If you post the table of what strengths correspond to what dice rolls, someone very well may be able to come up with a math equation to translate Magnitude X to diceroll Y. Is magnititude a stable value or can it fluctuate? That makes a difference too. In short, we need more data before we can help you. ^_^

For the most part most damage rolls are 1d10+x but as I said in my original post the Magnitude value of a Horde adds additional dice to the damage. So a Magnitude 10-19 Horde would add an additional 1d10 whilst 20+ is 2d10 damage. I'm not looking at the Macro to intuitively know what the Magnitude is and how it affects the additional damage die - I'm pretty sure that would be a function for the API - I'm hoping that it's something that can be added in due to a query. For example, to make a ranged attack with modifiers the Macro I have is "bla bla bla +?{Modifier|0}" this makes a pop-up window appear when the Macro is used which adds a value to the dice roll. It's something along the lines of the above that I'm looking for but replacing the value with a number of extra dice to roll.

Then try blah blah blah +?{Extra dice?|0d10} and then replace the 0 with the correct number at runtime.

Or: Blah blah blah +?{Extra dice?|0}d10

That works too ^_^

That works perfectly. Thanks for your help.