Hi Mark - if you turn on "Straight Snap" on the bottom toolbar it will help you with these kinds of axis-specific moves. When Straight Snap is engaged all you need to do is move your mouse nearby the x-axis line and it will then snap the movement onto that axis, it will show a dashed construction line type display going along that axis when it kicks in.

It works with any of the x, y, or z axis lines, just move your mouse nearby any of them to lock on to them and it works with either movement (like dragging an object) or with drawing tools to draw lines that are along an axis direction.

So anyway that's why there is no script for it, because the Straight snap function already handles this type of stuff, no special scripts or extra keystrokes are really needed for that.

Here is a previous demo and additional explanation:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3201.2

- Michael