= or <-

Dear R-users,

I have written a short VB application to clean and format my R code. 
Everything works fine except one small issue that I did not expected; it 
is related the automatic replacement of assignment signs from "=" to 
"<-". Most functions or arguments seem to accept either = or <-, but 
some don't (e.g.  ls(all=TRUE)). The result is that my supposedly clean 
codes do not run anymore :-(
Is there a way to know the list of arguments/functions that do not 
accept "<-" signs ?

Thanks in advance.

Sebastien