A computer input device includes a scrolling apparatus that includes a rotatable scroll wheel and a scroll wheel locking device. The scroll wheel locking device is activated when the document being scrolled reaches its end. When activated, the scroll wheel locking device prevents further rotation of the scroll wheel in the direction that would normally be past the end of the document, but permits rotation of the scroll wheel in the opposite direction towards the other end of the document. The scroll wheel locking device includes lockable wheel rotatable with and spaced from the scroll wheel. The lockable wheel includes angularly spaced pins. A tri-position lever includes locking elements engagable with the teeth to cause unidirectional locking.