Hi Andrew,
I don't think any Excel-to-HTML converter is going to help you convert the formulas in the cells into Javascript or script that runs on the web server (like ASP or PHP).
You have two options:
1) Easy but lazy way: Provide your users the link
http://www.saweather.net/forecast/Lendex.xls as a download. They can then use it only if they have Excel installed.
2) Difficult but proper way: Convert all spreadsheet formulas into ASP or PHP functions which run on the web server. You can then use HTML controls (drop downs, text boxes etc) to send (post) parameters to your server-side functions, which then process and create the HTML result on the fly and send it back to your users' web browser. This is how most websites (including this one) work.