Default application Excel and not Numbers...

I check my email from home (via Outlook Express...arghh). I have Excel based files I need to open and work with/manipulate data, etc. Every time I open these files, it opens the files in "Numbers". I have Excel in my applications and want it to open these files in Excel. I tried seeing if there was an "open with" option but could not find one. Can someone please help so my default reader for spreadsheets is Excel and not Numbers?

Thanks! Please email me with an answer. kc1st@me.com