There is no built in way to do so. You could possibly do it via MySQL directly via ALTER TABLE but you’d have to write custom code to take advantage of this yourself. Another option is to create a new table where each set of data references a certain post. Yet again, you’d have to manage everything yourself.
My suggestion: use a plugin like Meta Box or WP Alchemy to use the custom field system that’s already there. Either one creates a meta box of fields that’ll save the custom post meta for you