Hi,
If I understand exactly, whenever you click on an list item, a popup appears and you want to disable the vertical list, when a popup is displaying?
If so, there are several options, see two of them:
a) VerticalList.Enabled = false; <- disables the list and also its behaviour to touches, while a popup is showing
b) create an simple touch handler on top of the vertical list, which eats every touch (as long as it is enabled), which could deflect the touch event to the vertical list, if no popup is showing
HTH.
Chris