After learning the difference between "whomever" and "whoever" in this class, I constantly check other people's writings to make sure that they used the correct word. In the Wellsville Daily Reporter, I came across an article that used "whoever."
http://data.grammarbook.com/blog/whowhomwhoeverwhomever/whoever-v-whomever/ If you were to read this website it would tell you that whom=him and who=he. If you didn't know which one to use (whomever or whoever) you could break down the sentence in the above image like this, ______ is coming in that role at any given day.... If you were to place him or he in the blank spot, you would be able to tell that "he" makes more sense, therefore "whoever" is correctly placed in this article.