"The quote presented above is in no way a firm contractual bid.
It strictly provides you with an "approximate" cost for your project".
That looks a good way of doing things John, this would cover the issue of poor access. I often price at a £1 per window then if it comes to £13 I charge £12 etc or some times they may have less windows so my minimum charge applies. All this would have to be written in to the program. How easy would that be? What values would you add?