I think I understand.

My main in Account 3 would have it's Port, 1900

Then on Account 1, I connect to Port 1900.
Then on Account 2, I connect to Port 1900.

So:
(Account 1: Port 1901) --> (Account 3: 1900) <-- (Account 2: 1901)

Next Question.

Account 3 (tank) would have A White List pass keys "F G H and Space"

Suppose Tank 3 has established agro (just doing a spam of 1, 1, 1 button /castsequence.

I would like to control (dps Shadow Priest) Account 1's keyboard.

In Account 1, I want to White List pass keys "1 5 6 and \ (backslash)"

While in control of Account 1, I would do a sequence of 1, 1, 1, and (5 or 6, or \)

(5 and 6 does Mindflay, and \ is a Taunt macro of the tank in Account 3.

Question: So, does Account 1's Key Pass White List go to both Account 2 and Account 3, from Account 1?

I was hoping that while in Account 1's keyboard, I can have my keys passed to Account 2.

Account 2 will interpret:
Key 5 = Heal Account 3
Key 6 = Heal Account 1

I don't want to deal with going over Account 2's keyboard to heal. I want to heal remotely from either Account 1 (dps) or Account 3 (tank).