Finding out which functions are called within a given function

Possible Duplicate:
Generating a Call Graph in R

I'd like to systematically analyze a given function to find out which other functions are called within that very function. If possible, recursively.

I came across this function in a blog post by milktrader with which I can do something similar for packages (or namespaces)

listFunctions <- function(
    name,
    ...
){ 
    name.0  <- name
    name    <- paste("package", ":", name, sep="")
    if (!name %in% search()) {
        stop(paste("Invalid namespace: '", name.0, "'"))
    }
    # KEEP AS REFERENCE       
#    out <- ls(name)
    funlist <- lsf.str(name)
    out     <- head(funlist, n=length(funlist))
    return(out)
}

> listFunctions("stats")
  [1] "acf"                  "acf2AR"               "add.scope"           
  [4] "add1"                 "addmargins"           "aggregate"           
  [7] "aggregate.data.frame" "aggregate.default"    "aggregate.ts"        
 [10] "AIC"                  "alias"                "anova"               
....
[499] "xtabs"   

Yet, I'd like a function where name would be the name of a function and the return value is a character vector (or a list, if done recursively) of functions that are called within name.

Motivation

I actually need some sort of character based output (vector or list). The reason for this is that I'm working on a generic wrapper function for parallelizing an abitrary "inner function" where you don't have to go through a time consuming trial-and-error process in order to find out which other functions the inner function depends on. So the output of the function I'm after will directly be used in snowfall::sfExport() and/or snowfall::sfSouce.

EDIT 2012-08-08

As there's been some close-votes due to duplicity, I'll check how answers can be merged with the other question tomorrow.