controlling rigidbody 2d

Hi,

I've tried a lot of ways without success, please help me!

I need to move and object that is falling from the top of the screen due to gravity Scale (it has a rigidbody2D and a boxcollider2d components attached).

I've created two GUI.Button , a left and a right arrow.

and the idea its very simple, when the user taps one of those , the object has to move -1 or 1 (depending on which one the user taps) in the x axis, so i can chose where the object will land.

as i said i've tried a lot! still don't know what am i doing wrong. I succeeded when trying with an object that hasn't any component attached, using :

myobject.gameObject.transform.Translate (-1,0,0); (for the left arrow)

but with it comes to objects affected by physics it does not work, but it compiles! so i've got no idea what do i have to change!

please help me!!