[Newbies] before methods

[Sean Allen]

I've been working on some code using Proxies to step in front of  
method calls and now have an explosion of Proxy objects that
aren't doing anything to make the design clearer. Far from it ( see  
previous thread 'locking' an object ).

I've come back around to my initial inspiration for the design...  
CLOS's before, after and around methods.
Is there are a way to get the same functionality in Smalltalk without  
using a Proxy class?

In order to make it work, I'd have to be able to hook in to the  
standard vm message passing which all
seems to be implemented in primitives which doesn't leave me very  
hopeful that it can be done,
however, the rewards in my case would be great, so I'm here asking...

Is it possible to implement before, after etc methods in Smalltalk?