Return on investment calculator for medical imaging equipment

Looking for a return on investment spreadsheet for dental X-ray equipment. We sell X-ray units to dentists and Hospital. I need to select a specific X-ray machine from a list of around 6 models. Add a few options and support agreement to give me a total price. Then, we ask the dentist how many scans per day he would do on average, how much he charges per scan, Interest rate on lease, number of years and residual. This should give him a monthly cost to finance and run the unit along with his earnings from the machine. We will need a tab in the spread sheet for prices of machines and options. I would like to turn this into an app for our sales guys eventually. Also looking at putting this ROI calculator up on our web site.