trace(..., edit=TRUE) with external editor

I am using an external editor (TextMate) with R and I want to be able  
to successfully use trace(function, edit=TRUE).  Has anyone been able  
to do this?

I am using Leopard, R version 2.7.0 R.app GUI 1.24 (5102).  I've tried  
it with other external editors as well.  For example, set an external  
editor (TextEdit, for example) in the Preferences and then try  
"trace(plot, edit=TRUE)" and add something like "message('hi')" to the  
top of the function, save and exit the text editor.  Then call  
"body(plot" in R - the added line is not there.  Is it not possible?   
Thanks!