Pickaxe destroying multiple blocks

idk what to do, I made a pickaxe and am trying to make it mine multiple blocks at once, I am trying to make a procedure under the "When block destroyed with tool" to do so. I used the command "Remove block at (x)(y)(z) and drop at (x)(y)(z)" filling them with the desired coordinates (x - 1, y - 1, z - 1, etc.), yet when I go in game it never works and idk what to do. any help would be greatly appreciated.