There's no way to send MouseWheelForward or MouseWheelBackward events. Those words can be used only as triggers of hotkeys.

It was done this way because the mouse wheel is conceptually different from all other keys and buttons. (I'll explain why this is true in a moment.) As a result, it was easy to add "trigger-only" support, but it would be much more work to add a way to send mouse wheel rolls. Changes to keywords would be required and additional info would have to be sent from one PC to another.

Mouse wheel rolls are different because when the mouse driver and operating system report them to programs like HotkeyNet, the message says, "the mouse wheel was rolled forward (or backward) a certain distance." There's a magnitude involved -- how far the wheel rolled. But there's nothing like this with other keys and buttons.

Therefore to send a mouse wheel event, the program would need a keyword like this:

Code:
<Roll Forward 8>
Where 8 is the number of clicks to roll. This would be easy to add to the program. But this only works if you know in advance how far to roll, and that's not how people want to use the feature. They want the program to broadcast rolls. That means the program must notice how far you rolled the wheel when you actually use the mouse, and then it must copy that magnitude to other windows.

For example, people want to write something like this:

Code:
<Hotkey MouseWheelForward>
   <SendPC REMOTE_PC>
      <SendWin MY_WINDOW>
         <Roll %Trigger%>
In order to make this work, the program would have to record the magnitude of the roll in an implicit variable and send that info to other computers.

In the new program, %Trigger% will be replaced by a real variable rather than a text macro, and it will be easier to do this.

Edit: Also, the new program will do pure event broadcasting which will make this extremely simple.