How to calculate BMW Select payment?
 

I'm negotiating on a couple different car options right now as my X3 lease nears its term and considering Select (I know, I know).

Anyway, more to the point, I've searched and searched... but cannot find a good spreadsheet or equation on how to manually calculate it myself.

Also, I seem to have confirmed that finance APR specials DO apply to the interest rate portion of Select, correct?