On an X10, how do you change the unlock sweep from starting at lower right and going to the upper left, to starting at the lower left and going to the upper right?

Now this is not the custom 4-position unlock code; I'm referring to the 'arcing sweep gesture' that's necessary to 'wake-up' the screen, after it automatically goes to sleep.

The sweep gesture is prompted by tapping the power button on the top of the phone.

Thanks for any and all replies.