You can either embed a picture of the table and put it in the forum... or upload it somewhere like MegaUpload and provide the link.
I'm fairly sure the forums don't support excel integration.
You can zip your Excel file and attach it to a post, but I don't recommend that. Instead, you should try importing into Google Spreadsheets (here's how). Then, you only need to post a link to the spreadsheet page, which will be automatically updated when you revise it.
