In CorelDRAW Graphics Suite X4, whenever you use the Mouse Wheel the document zooms in or out.
But you can also use the mouse wheel to scroll vertically and horizontally in your document.
The trick is to use the "Ctrl" and "Alt" keys. With the "Ctrl" Key pressed you can scroll Horizontally and with the "Alt" key you can scroll Vertically.
You can also press the mouse wheel and move you mouse to navigate Vertically, Horizontally or Diagonally.