This might not be possible but I thought I would ask. Is there any way to append public functions to a class with out editing source code?

What I mean is I am almost finished creating a bunch of custom functions for STL strings and it would be really nice to have be a part of any var that uses STL strings. For example I have a trim function, it would be nice just to do this:

Code:
string s;
s = "blahblah";
s.trim();
Or is there another way to do this that I am not thinking of?