UPDATED 17/3/2014
Features
*Damage track and modifiers
*Modifiers for attacker's movement
*Environmental modifier calculations such as range, visibility, glare and wind
*Environmental modifiers steps (so if your 2 biggest environmental modifiers are -1 then it becomes -3; 2 at 6 become -10, etc
*Gear modifiers for environmental modifiers (e.g using ultrasound will reduce your visibility and light level penalties to 0 at 50 meters (or less) but does nothing at 51 meters.
*Range penalties calculated on weapon types (i.e Light or heavy pistol; SMG, etc)
*all smartlinks and laser sights are implemented (I think..) and it matters whether their wireless is on or off
*Aiming actions are implemented, as well as the way they interact with Willpower and image magnification.
*Recoil compensation for strength added and progressive recoil implemented.
*Added a purdy picture to make it all Shadowrunny. Cleaned it up and protected sheet. The password is 'Shadowrun' if you want to edit it or play around with it.
Assumptions
1) Recoil simply counts bullets fired. Every time you enter your variables you get a bullets fired (since last reset at the top of the screen. Enter this into the progressive recoil field for your next IP unless you reset recoil (adding an 'Aim action' will ignore the progressive recoil field)
2) You are only using 1 weapon and only benefit from 1 laser sight/smartgun system
3) Implementing individual weapons could be done so damages calcs and defense modifiers can be reported. This doesn't outwardly appear to provide enough benefit to warrant the extra work.
This is a work in progress, it may not be perfect and some of the nerdier of you out there might find the logic hideous, but I'm only a casual excel user so be nice

Thanks to DMiller for fixing some of the formulae

Shadowrun Combat Pool Calculator