[Adam]

Originally Posted by M&M Guy

Hmm, that's not the way I learned it. "Whomever" should be the subject of a clause, while "whoever" is the subject of the verb.

Whoever and Whomever | Grammar Rules

It's just like the use of "who" and "whom." "Who" is used for the subject, and "whom" for the object.

example:

"Who gave the carrot to whom?"
answer:
"Whoever gave it to whomever."

At least that's how I learned it.