there are several ways of implementing an hourglass in emWin.
If it should stick to the cursor you could use the function GUI_CURSOR_SelectAnim(). You could use the default animated cursor (which is an hourglass) or create your own. Please refer to the API description of GUI_CURSOR_SelectAnim() in the manual.
If the hourglass should be drawn somewhere on the screen you could also draw a GIF-animation using the GIF related API.
A third method might be to use a sprite and draw it on the screen (this is more or less the same as a cursor).