The problem as I see it is that saving a spreadsheet as html only saves the values of the cells into web page format.
When you look at the sheet in a web browser, you can't use it like an Excel spreadsheet. You can't add/amend formulas or add/amend values in cells for the formulas to work out and display results. So a calculator spreadsheet will not be a calculator web page, it will just be a web page that shows cells with values in them. Any form buttons with macros or VBA module code assigned to them will not work, because the VBA code does not get converted to html when the spreadsheet is.
To make sure I am right I have just tested it. I have a workbook full of formulas and vba code which I re-saved as a web page. Using IE7, (Internet Explorer would have been more likely to work as it is part of the Microsoft family), I opened the workbook htm file.
All I got was a web page displaying my spreadsheet values. The sheet tabs were there and I could navigate to other sheets, but none of the cells were active, and so I couldn't change anything. None of my macros worked.
So it seems to me you are going to have to use another method, eg Java or one of the more sophisticated web page design methods.
Mark