Animation kerfuffle

Hello! I wanted to get into modding, and I have the idea of an item that rips through stone and dirt while leaving the rest of the blocks alone. so, I made one idle sprite, for when the player is just holding it, and one grinding sprite animation. the problem is, I'm not sure how to make the item use the grinding animation when in use. think, like, the bow. when you hold down right-click, it plays the charging animation, then goes back to idle when right-click is release.