Get a command block: /give @p command_block

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Put this in chat: /scoreboard objectives add left dummy

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Repeating Command Block: /scoreboard players set @a left 1 {Inventory:[{Slot:-106b,tag:{display:{Name:"Cool Thing"}}}]}

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Chain Command Block: /execute @a[score_left_min=1] ~ ~ ~ YOUR COMMAND

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Last Chain Command Block: /scoreboard players reset @a left