No method to set globals in dial plan

I am adding some modified modules that provide specific features for our freepbx installation (2.2.1). However some of these modules require not only to add global variables to the dial plan but also to modify these globals while asterisk is running. The extension.class file seems to contain a method only to add global variables to the dialplan (setvar()/set()). There needs to be another to set them as follows:

class ext_setglobal {
var $var;
var $value;

function ext_setglobal($var, $value) {
$this->var = $var;
$this->value = $value;
}

function output() {
return "Set(".$this->var."=".$this->value.",g)";
}
}

Best Regards
Nick