I recommend you to check out a timesheet template that I am currently using. It keeps track of all the hours you are working. In fact it is designed to do that for multiple employees, however, I think you can adjust it to a single user as well. If it doesn't work for you, at least it can give you an idea on how to create your own spreadsheet.

You can find it here: http://spreadsheetzone.com/templateview.aspx?i=109