Didn't have much luck in searching for this, so I figured I'd ask.

I have a spreadsheet I need to integrate to Salesforce for a client which is doing some propriatary calculations to output some leasing values for an opportunity. My initial plan was to simply recreate this logic in Salesforce and have the system auto calculate it and output it to a field on an opportunity, but the leasing company won't unlock the spreadsheet or allow anyone access to their calculations.

Is there any other way to pass values to and from a Spreadsheet? I wasn't finding any obvious answers or apps, which I think is usually because Salesforce aims to replace the spreadsheets. The client and I really want to get rid of the spreadsheet, but since we can't attain these propriatary calculations we're stuck with it for the time being and are trying to find a solution other than all the copy/pasting that otherwise needs to happen between Salesforce and Excel.