Notation question

Hi,

I understand chess notation for the most part, but am wondering about one thing.

How do you notate when you have two of the same pieces that can go to a square? For example, you have a rook on a4 and c4. They both can go to b4. Let's say that you move the rook on a4 to b4. Normally you would write Rb4, but in this case, it doesn't show which rook you put there. So how do you write that down?

1.Rab4, or 1.Rcb4.

Thank you!

The extra letter or number before the intended square is usually placed to distinguish between two or more possible moves.

With letters:

Or with numbers:

Or even these, with both letters and numbers:

Thanks eric0022 for the clear and elaborate explanation! 

I also have a similar question. 

How do you notate a move order sequence where the number, say 4. f3 is irrelevant. 
Im looking at an exchange that is waiting to happen so when i write the notation how do you seperate white and blacks move simply like you do with the 4. or 4...

Not so sure, but do you mean things like these?

1. e4

Intending a possible Qf3 and Bc4 within the next two moves.

No, im thinking notation thats not linked to a move number. 

Say you have a rook pinned to the king and the rook can take the attacking rook but you dont know when its going to happen. When you write notation for a possible tactic you dont know the notation number so to speakm, so how would you write that?

Oh, this I am not too sure but I would write everything without the number moves, stating who plays the first move in the list.

And if I am not sure of the exact time in which the move is going to be made, I would not write the move itself, but rather, like this.