The TBM_GETTICPOS message retrieves the current physical position of a tick mark in a trackbar.
TBM_GETTICPOS wParam = (WPARAM) (WORD) iTic; lParam = 0;
Returns the distance, in client coordinates, from the left or top of the trackbar's client area to the specified tick mark. The return value is the x-coordinate of the tick mark for a horizontal trackbar, or the y-coordinate for a vertical trackbar. If iTic is not a valid index, the return value is -1.