int pascal SetScrollPos(HWND hBar, int nBar, int pos, BOOL fRedraw)

  This function sets the thumb position of the specified scrollbar to
a certain position.

Parameters
  hBar is the handle of the scrollbar.
  nBar indicates which scrollbar you want to operate on. If nBar is
   SB_CTL, then the hBar parameter contains the handle of the actual
   scrollbar you want to manipulate. If nBar is SB_HORZ, then you want
   to manipulate the horizontal scrollbar which belongs to window hBar.
   If nBar is SB_VERT, then you want to manipulate the vertical
   scrollbar which belongs to window hBar.
  pos is an integer value which must lie in the scrolling range
   specified by the scrollbar's minimum and maximum values.
  fRedraw is TRUE if the scrollbar should be redrawn after the thumb
   position is changed, FALSE if not.

Returns
  This function returns -1 if pos is out of the scrollbar's scrolling
range. Otherwise, the value of the old thumb position is returned.