2 objects 1 bone

ok so i want to animate in roblox, moon animator will not use the bones giving by blender, so i need to make it so i can move a seperate mesh to beform the thing i want to animate,

long story short need to make it so i can move a cube and move some mans arm in the process, how?

and no not touching the bone at all, just moving a block that is some how conected to a bone that will move another thing