Not exactly sure what you are asking here, but everything you need to know about RNG for Diamond, Pearl, Platinum, Black, White and Emerald can be found
here.
If you are unsure of what RNG is, here is a gross oversimplification:
As you know, Pokemon you encounter have random stats. Like for instance, Nature, Ability, and Shininess. A good way to look at it, is stats that a Pokemon will receive go through a formula, or a
Random Number Generator (RNG). And in this formula, there are several random numbers. These numbers help make sure that every Pokemon you encounter is different, and will have varying stats. To make Pokemon even more unique, the game carries a number called an SID, or a 'Secret ID'. Your SID is created once you start the game for the first time, and is totally invisible. The formula then takes those random numbers and your SID to create totally unique, and random Pokemon.
However, at least in the digital world,
there is no such thing as a random number.
So. In order for a computer to create pseudo random numbers, it has to look at constantly changing variables. Instantly, the
time of day may come to mind, or
the number of steps taken in game. It may seem random, and it absolutely is when you are running around doing your average gameplay, but these 'random' numbers are things we can control.
Ok, ok, we already know that we can control most of the 'formula', but we still need to know our SID to fully manipulate what stats our Pokemon will get. The SID is a tricky number to deduce; as I said, it's invisible. However. If you have captured a shiny Pokemon, you can 'reverse engineer' your SID. Kinda like and Algebra equation where you 'solve for X'.
As an example, let's say the
RNG is this: X+2=Z. Now, X is your SID, 2 is the random number, and Z is the caught Pokemon. Hypothetically speaking, if you say the shiny Pokemon's stats is 4, you would get X+2=4. So in this gross oversimplified example, your SID would be 2. I'm not 100% sure how you are
actually able to deduce your SID with a shiny, but I'm pretty sure it's done similar to this, just, way more complex.
Once you know your SID, you are able to plug it and the other variables necessary into the RNG. Then you can figure out what time, number of steps, etc. is necessary to create the Pokemon with the stats or shininess that you want.
However, to clarify, in Black and White, you do not need your SID to generate IVs, or 'Individual Values'. (If you are unfamiliar with IVs,
HERE is an awesome tutorial by Pokebeach's Chariblaze.) However, it seems to me you are interested in getting Shinys, so you will have to have captured a shiny Pokemon in the wild.
This post was not meant to teach you
how to RNG. Rather, to give you an idea on how it works.
I suggest looking at some videos, or tutorials like the one I linked you at the top to get the full idea of it, and maybe do it yourself.
