int pascal GetScrollPos(HWND hBar, int nBar)

  This function retrieves the current value of a scrollbar's thumb
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.

Returns
  This function returns the current thumb position of the scrollbar.

Example
  Retrieve the thumb position of the window's horizontal scrollbar
int iHPos;
iHPos = GetScrollPos(hWndMain, SB_HORZ);