[ESS] several R versions

[Kasper Daniel Hansen]

Hi

I am currently using R with ESS v5.2.9 under Mac OS X using Carbon  
Emacs (Emacs v. 22.0.50.1).

I have started to use two different R versions. The standard stable  
release is called using R in the shell. Then I have the development  
version which I start using R-devel (this is a symlink in /usr/local/ 
bin).

I would like to use both versions in Emacs, eg. doing something like  
(all this exact form is not really relevant)
   M-x R
and
   M-x R-devel

I assume that it is quite easy to do so, but how?

Kasper