Whose Rule is it Anyway?

I learned a new grammatical rule the other day and it interested me so much, I figured I would share!

I have never been able to use "whom" correctly. I have a friend, though, who is an editor for a local publication and she revealed to me the great SECRET. The secret is this:
(Looking around furtively to ensure no one else is listening)
The secret is: if you ask the question about a man, how would it be answered? If the answer is "he" then the correct word to use is "who". If the correct answer is "him" then use "whom". Finally, (and I figured this part out all on my own) if the answer is "his", use "whose".
The end letter of h(e), hi(m) and hi(s) determines the ending of wh(o){the vowel}, who(m) and who(se) respectively.

So, [who] does the cat belong to? Him? It should be "Whom does the cat belong to?"

[Who] is going to the park? He is? And this one is correct!

[Who] rule is it anyway? His?

WHOSE rule is it anyway?

Thus ends the English lesson for the day!

I was so very excited about learning this that I HAD to share!