CSV or comma-separated-value is the most basic way, but should work with almost any spreadsheet.
It generates a text file with the content of the spreadsheet. You need to use the “Import CSV” feature of your favorite spreadsheet to load the file. You should then have a working simulator, in which you can change the input values and have the output values automatically computed.
This method is validated for importing in Microsoft Excel, OpenOffice.org Calc and LibreOffice Calc.