WinCC Flexible 2008

Hi,
I will use WinCC flexible with OPC server in desktop PC for logging some data.
I can display log data at screen but can't select to specified time or date. I must use backward button.
Please help, if I select some date/time then graphic will displayed to selected date/time too.
Thanks

I think it is not possible.
There is a system function, TrendViewScrollBack, but it says it cannot work in a script.