Lighting, Light Fixtures, Ceiling and Exhaust Fans - 4 switches, 2 lights

I am pretty handy with electrical wiring, but cannot find a diagram to cover this situation. I want to control two lights in a hallway from 4 different switches. The area is down to the studs so I can bring the power in at any point, but would prefer anything but S1. Could someone either direct me to a diagram or provide one? My book only goes to 3 switches.
The layout is actually....S1, bottom of the stairs...S2, top of the stairs,...S3, around the corner, beginning of the hall....light, light, in series,....then S4 at the end of the hallway.
Thanks!

Bring power to one of the switches.
Run 14/3 from switch to switch to switch etc .
Run 14/2 from last switch to light to light to light.
Use this drawing and just add as many 4 way switches in between the 3ways as required. Wire additional 4ways exactly like the single one present in the drawing.
Add additional fixtures by connecting black to black and white to white.

http://www.selfhelpandmore.com/switchoutlet/4way/4waylast.htm

Piece-of-cake, then, thanks a lot!