Handler for wheel up/down events.
| OpenLayers. | Handler for wheel up/down events. | 
| Constructor | |
| OpenLayers. | 
| control | {OpenLayers.Control} | 
| callbacks | {Object} An object containing a single function to be called when the drag operation is finished. The callback should expect to recieve a single argument, the point geometry. | 
| options | {Object} |