I've been trying to figure out how to use the "iteration" feature. I
have it checked in the preferences, but can't seem to "turn it on" in
the actual formula. I'm doing something wrong. The situation is pretty
simple:

Cell P4 contains the number 1.0001.

Cells M4:M500 contain numbers.

Cells N4:N500 contain those numbers multiplied by the value in cell P4.

Cell N501 contains the sum of N4:N500.

I need to increase cell P4 in increments of .0001 until N501 equals
8,800,000, or gets as close as it can without going over.

I've tried it using something like, for cell N4:

IF($N$501<8800000,N4*$P$4)

And it just does it one time and sits there. I've tried playing with
Solver and Goal Seek and can't make it work. Can somebody help?