short answer... no

I don't know of any way of modifying the core classes without hacking the core, or extending the classes with your own.  Can you not use a global function for it?

Thanks for the quick reply.

let me know where will I define/create a global function?. (Since I'm new to elgg, sorry, if this is silly)

start.php of your plugin. You can register your functions in a seperate library and can load it as and when needed using elgg_register_lib() and elgg_load_lib(). Take a look at some core plugins.

Someone please reply.

Me to!