Converting transfer function from s-domain to z-domain

[Jason Rupert]

By any chance is there a function to convert a transfer function from s-domain 
to z-domain?  

For example, assume I have spring-mass-damper second order system transfer 
function in the s-domain:
http://wikis.controltheorypro.com/index.php?title=Second_Order_Systems

Is there a function in Octave or one of its packages that would allow me to 
automatically convert that over to the z-domain? 

Thanks again for any insights and feedback.