Clist scrolling to non existant line

["Tom Knowles" <tom peters co uk>]

Using a Clist within a scrolled window in a touch screen system.
I have added  a page up/down facility to rapidly negotiate clists. There
seems to be no obvious way of knowing if a non visible line is actually
there, and selecting or moving to that line seems to cause strange behaviour
( I have to leave the up/down widget and redisplay to regain movement). With
the touch screen I cannot use the scroll bars. Is there no simple way of
knowing how many rows there are?
Many thanks
Tom