[jQuery] How to save "this" context in callbacks

[Alexander]

Goodday!
Could anyone tell me how to save "this" context inside callback?
Here is simple example:

var myClass = jQuery.Class.create({
        init: function(){
                this.value = "value";

                // callback as argument:
                someExternalFunction( function() {
                                this.setValue(); // PROBLEM: "this" is not 
myClass pointer
anymore!
                        } );
        },

        setValue: function () {
                this.title = "new value";
        }
});