An assembly includes a mouse pad platform forming an upper mouse pad platform surface suitable for operating a computer mouse, an armrest platform forming an upper armrest platform surface suitable for supporting a forearm of a user while operating the computer mouse, an adjustment plate fixedly coupled to an underside of the mouse pad platform and an underside of the armrest platform, thereby connecting the mouse pad platform and the armrest platform, and strap mounts on at least two of the mouse pad platform, the armrest platform, and the adjustment plate, the strap mounts being suitable to couple straps to the at least two of the mouse pad platform, the armrest platform, and the adjustment plate. The adjustment plate is selectively positionable along the underside of the mouse pad platform and selectively positionable along the underside of the armrest platform allowing adjustable spacing between the mouse pad platform and the armrest platform.