Lease Calculator Program or Calculation Site

There are always so many variables in leasing and I never seem to find "exactly" the same deal. Does anyone know of a place on the web where I can access or download a leasing calculator that would allow me to put in each of the numbers, fin. factor, sale price, term, etc. and then come up with an accurate lease calculation. I have always found it extremely helpful to pull out my laptop or tablet and "independently" calculate the numbers and see exactly how close they are to the mo. pmt. being offered by the dealership. I'm not questioning anyone's integrity, it was just that with the program that I used to have (lost when computer crashed), my calculations always seemed to yield a lower payment/mo, and after the dealership rep. "recalculated" his figures they seemed to coincide with the ones that showed up in my program. Secondly, I notice that most leases are now requiring a d/p (aka "Capital Cost Reduction") for the lease. My purpose in a lease is to conserve capital, and to amortize all costs over the period of usage. In my old undergrad days as an Econ & Fin major that was what a lease was all about. Are there lessors that are more consistently leasing the vehicle w/out the CapCostRed?
It is time for the partners to bid out our new company cars & look for the responses to our RFP's. Our program allows us to lease any vehicle that we like within certain criteria, which are generally applicable to the overall cost of the lease, including time value of money. Of course, since I haven't done this in a while, I am open to any and all advice that any knowledgeable individual would be willing to provide. We generally look for high performance sedans, although due to some geographical considerations my last lease was on an SUV with protective systems, aka "Armored" so it was an unusual deal, and I no longer have that requirement so a more typical leasing process is available to me.
Comments
This is the calculator I've been using over the past few days. My numbers come to exactly what others have confirmed when posting on the forum.
http://www.bankrate.com/calculators/auto/auto-lease-calculator.aspx
http://www.leaseguide.com/calc.htm
We have one too:
Auto Lease Calculator
And we have a good article about how to use a lease calculator with an example that's clear enough that even I almost understand how leasing works.
Calculate Your Own Car Lease Payment