goffi on "More actions?"

May be this question has been already posted but i don't found anything.

Few days ago i wrote a little plugin and what i want to do has been impossible with the actual filters or actions.

Why don't put a callback in the begin and end of the functions? Obviously returning errors and exit from the function before the execution of the body.

I mean some thing like this:

function wp_function(...) {
if( do_action( 'wp_function_before', ... ) ) {
return ERROR;
}

// body

if( do_action( 'wp_function_after', ... ) ) {
return ERROR;
}
}