How To Make Item Spawn When Player Uses Bow?

Hi I'm trying to make it so when the player fires a projectile from a custom bow, every third time he fires one, one of the projectiles spawn where he fired it. I have it triggered to "When Player Finishes Using Item" Trigger. Here's the code, what am I doing wrong?

Here is a screenshot of the code: https://postimg.cc/Ny0V5xJY
Thanks