Ahh, function I see you set the empty array as a float variable, from what I know of MEL you don't have too ? The script worked, although after I run it a few times it fires an error on line 8 ? Where did you get MPosition ?
If one position of a point is here; Mouse position : 947 540 0. Then it must be possible to take that point and select, like symmetrical do the same thing on another point except opposite world coordinates by storing it into a empty array, selecting another point and applying the same world coordinates to the other point…