First, we'll create an integer object that will hold the number of times our function has executed.

var counter = 0;

Next, let's create our function, we'll called it moveLeft().

var moveLeft = function() {
// our function code goes here.
}

Inside moveLeft, we'll write use the tween() method to move #bluebox to the left.

$('bluebox').tween('margin-left', (counter+1)*50);

Now, we need to increment the counter every time the function is called. We'll use the following line of code, which will execute as soon as our box has finished the animation to the left:

counter++;

Let's now use periodical() to execute the moveLeft() at...