IMHGuess, it would depend on what you are programming. if it is the 1900AD series human brain on an IFR descent to LSALT you would need to re work it to allow for your change of track to ensure you don't smack into something solid.. .. .does that help/sound right? probably not.. <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> . .. .HJ