I have an excel spreadsheet that I want to post on one or more pages on my website. Using the text tool I can add the contents but without the formatting of lines and columns.

What do I need to do to include the formatting of lines and columns??

Have you just considered posting it as HTML?
http://www.maketecheasier.com/easily-convert-a-spreadsheet-to-html/

Depending on the version of Excel you can do a "Save as" and then select Web Page (*.htm,-.html).
It sounds like you may have already done this. If so save the page to your site and use an iframe in an html box.