As has been pointed out, 60% loadfactor is low, and though 100% is a little idealistic, you should be aiming for 80-85%. If you are not achieving this then you need to study the competition and adjust pricing. Spill modelling could also help you maximise loadfactors.
Pricing, frequency and capacity are really the only levers available, so you need to adjust accordingly.
As for your original question regarding spreadsheets, Excel should suffice for what you need.
It is unlikely you will be the only operator on the route, so it is important you figure out what your competitive advantage is, and where you feature in the market place: Great service? Low fares? or convenience?
Finally, you might find it doesn't work. If it doesn't - don't open the route and avoid one of the biggest pitfalls in aviation. You're not going to be Ryanair and won't create a sustainable market from scratch.
Hope this helps.
Last edited by minigundiplomat; 22nd November 2010 at 16:10.