Survival-Analysis: How to get numerical values from survfit (and not just a plot)?

Hi!

I came across R just a few days ago since I was looking for a toolbox 
for cox-regression.

I?ve read
"Cox Proportional-Hazards Regression for Survival Data
Appendix to An R and S-PLUS Companion to Applied Regression" from John Fox.

As described therein plotting survival-functions works well 
(plot(survfit(model))). But I?d like to do some manipulation with the 
survival-functions before plotting them e.g. dividing one 
survival-function by another.

survfit() only returns an object of the following structure

      n events median 0.9LCL 0.9UCL
55.000 55.000  1.033  0.696  1.637

Can you tell me how I can calculate a survival- or baseline-function out 
of these values and how I extract the values from the object? I?m sure 
the calculation is done by the corresponding plot-routine, but I 
couldn?t find that one either.

Regards

Bernhard