build spreadsheet, ratings to prices

I need a spreadsheet built to frame a market for horseracing betting. Points are assigned to each horse to give a total which is then converted into a price for each runner, The spreadsheet will need to show the bookmakers percentage per runner, and have the ability to alter the whole market percentage. True probability is 100% The further the percent goes above 100% the lower the prices. Alternatively the lower the percent value below 100% the higher the prices. The example below is an online application that does what i want the spreadsheet to do. To frame your own markets using the exclusive Expertform Performance Ratings simply: * Specify the Rating you believe each horse will achieve for today's race in the Predicted Rating column to auto fill the Predicted Rating column with the values from the other columns - click on that Column heading. (e.g. to enter the Expected Peaks for all horses click on the column heading Expected Peak) * Specify any bonus or penalty values in the +/- column. (eg. some analysts like to award jockey bonuses or penalties) Change the Percent value to your desired level * Change the Confidence level - if required (explained in detail on the Confidence Whats This pop up) * Click the Get Prices button to produce your final market with prices ** To adjust the weight carried up (eg. jockey may have to ride 1kg over) deduct 0.7 points off your predicted rating per kilogram over *** Remember each Rating point equates to half a length (2 points per length) **** To clear the Predicted Rating column and start again click on Predicted Rating ( the column heading)