Minecraft Block drop change no mods! (1.8)

Scoreboard Objectives: minecobble (stat.mineBlock.minecraft.cobblestone), cobble (dummy).
Command to create objectives:
/scoreboard objectives add minecobble stat.mineBlock.minecraft.cobblestone
/scoreboard objectives add cobble dummy

execute @p[score_minecobble_min=1] ~ ~ ~ scoreboard players set @e[type=Item,r=7,c=1] cobble 1 {Item:{id:"minecraft:cobblestone"}}
execute @e[type=Item,score_cobble_min=1] ~ ~ ~ summon Item ~ ~ ~ {Item:{id:"minecraft:diamond",Count:1}}
scoreboard players set @a[score_minecobble_min=1] minecobble 0
kill @e[type=Item,score_cobble_min=1]

Video:https://www.youtube.com/watch?v=xe6IDUiU-zo