on Banner Scrolled
This is invoked by BannerX when the current Banner is being scrolled.
Parameters
position
The index position of the current Banner being displayed. The next Banner at position+1 will be visible if positionOffset is 0.
position Offset
Float value in the range [0, 1) indicating the offset from the Banner at position.
position Offset Pixels
Same as positionOffset but in pixels.