Minecraft – How to use the scoreboard command in Minecraft 1.8.1

Since Arrows don't contain the data of what bow shot it from, we must mark the arrow as its being shot.

Setup:

/scoreboard objectives add Shot stat.useItem.minecraft.bow
/scoreboard objectives add Holding dummy
/scoreboard objectives add LightingArrow dummy
/scoreboard objectives add InGround dummy

Clock(20tps)

/scoreboard players set @a Holding 0
/scoreboard players set @a Holding 1 {SelectedItem:{tag:{display:{Name:"Lightning Bow"}}}}
/execute @a[score_Shot_min=1,score_Holding_min=1] ~ ~ ~ scoreboard players set @e[type=Arrow,r=2] LightingArrow 1
/scoreboard players set @e[type=Arrow] InGround 1 {inGround:1b}
/execute @e[type=Arrow,score_LightingArrow_min=1,score_InGround_min=1] ~ ~ ~ summon LightningBolt ~ ~ ~
/kill @e[type=Arrow,score_LightingArrow_min=1,score_InGround_min=1]
/scoreboard players set @a Shot 0

No, this is not possible (well, easily)

Minecraft sadly does not support insertion of scoreboard scores anywhere in a command, they can only be used in selectors (e.g. @a[score_myScore_=1]) or in the /scoreboard players test command.

However, there are a few (albeit complicated) workarounds. They work by running a bunch of conditional teleportation commands using distances decrementing in binary.

This command block modules fits your example, although I believe it uses the 1.8 command blocks. It shouldn't be too hard to adapt though, the mechanism is fairly intuitive.

However, that only fits your specific case. There is no general solution. 90% of the time you'll be able to do some binary version for that specific situation though, and if you ever make a good one, please let the community know :D