There are a number of ways you can achieve that. Here is one:
By pressing WIN+F1, the scroll wheel will turn once every half a second. Then you can press WIN+F2 to stop the scrolling.
Yet another approach is to use the ACrl.execAction() function to execute a scroll action with a more elaborate timing control and start/stop conditions.
You have lots of possibilities. It all depends on what you are really trying to achieve.