How can I detect the movement of a Listview?

For my current project I need the Delta movement of a list-view.
I'm putting in a tab-bar along the bottom of the screen which needs to scroll away and back when the listview moves down or up (respectively)
For a visual aid, take a look at how the bottom-bar in the Android web-browser operates.

There are no variables or events in listview that I can find that will do this
adding a PanGesture over the top of the listview doesn't pick up vertical movement, only horizontal.

The only interim solution I've found is to detect direction of travel using ItemAppearing. but that doesn't give the smooth 1:1 movement I'm after, only triggers an animation.

Suggestions?
Rowan