[wxhaskell-users] Use of Ptr type for calling treeCtrlHitTest

[<ber...@ic...>]

I would like to use the function

treeCtrlHitTest :: TreeCtrl a -> Point -> Ptr CInt -> IO TreeItem

but I cannot find out from the wxHaskell documentation how to create / 
use the Ptr argument, which stands for an "out" parameter.
Can someone tell me how to create a value of type Ptr CInt to apply it 
to the treeCtrlHitTest function?

Thanks,
Bernd