Percentage Macro Question

Hi, I just had a quick Macro question, how would I go about calculating a percent reduction? If I wanted one individual to roll damage versus a target and for the damage to be reduced by the targets damage reduction how would I go about it? What I have so far would be something like: /r 1d8+9 - [@{target|DR}*result of 1d8+9] but I don't know how to have the macro use the result.

Assuming that @{target|DR} is a percentage expressed as a decimal ie 25% = 0.25. you could use something like this: [[round((1d8+9)*(1-@{target|DR}))]] Additionally you can leave out the round or use floor to round down to a whole number or ceil to round up to a whole number.