Lightsaber: Adobe AE - How to hide a part of the solid when its moving behind an object?

I am using Ryan W´s guide to create lightsabers in Adobe After Effects. Its working perfect, but how do I hide a part of the solid, when it is moving behind an object (the body)

 

From Ryan himself:

HANDLING OBSCURITIES
So far you know how to keyframe animate a mask to cover your refrence prop. Cool. For simple shots you should be covered. But what about shots where your saber swings behind something or someone? This is how to handle these obscurities by making a new mask that essentially takes away the parts of your lightsaber mask that shouldn't be visible.
Go back to the beginning of your footage and move forward until you come the first frame that something blocks or obscures your lightsaber that causes it to be "broken" and then move back to the frame right before it.

In the toolbox, click the pen tool.

Draw a new mask off of the footage's canvas with 5 or 6 points. (If you know what you're doing, you will know how many or how few points you will need here, 5 or 6 is just a generic number of points to use for this example)

In the switches/modes panel of the timeline window, set the new mask's mode to Subtract.

Click the triangle next to the new mask's name in the timeline window, and then click stopwatch for Mask Shape.

Using the Time Controls palette (Windows > Time Controls) move forward to the next frame. (This should be the frame where the lightsaber is first "split in two")

In the toolbox, click the Selection tool and then click anywhere off of the canvas in the footage window to deselect all the currently selected points on the mask.

Move (click and drag) the points on the new mask to define the area of the lightsaber mask that should not be seen.

Using the Time Controls palette, continue moving through time and keyframe the new mask to hide the part of the lightsaber blade you do not want seen.

When you come to the frame where your lightsaber should no longer be obscured, move all the points of the subtration mask off of the canvas. (Make sure that the frame before this one has a kayframe set for it)

Note: If your lightsaber becomes obscured again later in your clip, you do not need to make a new subtraction mask, instead simply keep using the same one, making sure you set keyframes of the mask off of the canvas before and after it is on screen.

 

Thanks RW... your the master!