Save a Spreadsheet ?

I can not remember how to save a spreadsheet as a templete so that all you have to do is open it up and type each time and it will save without changing the orginal document. Does anyone remember how to do this or any other suggestions to set up as easier way to bill customers ?

http://www.ehow.com/how_13117_create-spreadsheet-template.html

???

other than that, I’d say set the file attributes to read only so it cannot be saved