you do not have to use repeating fields for this purpose, but related records, each holding its date and reading.
And such a related table as suggested by raybaudi can be sorted as needed and you can add as many new related records as you need--thus meeting both of the your requirements and things that really can't be done with repeating fields.
Hint: If you are using repeating fields to get a horizontal row of values, this can also be done with a table of related records--using the horizontal portal trick.
OK, i've done as you've suggested and created another table for the Date and Meter Reading, which works fine.
Previously the table (with the repeating field) was displayed via a portal in a different table without problem. But now i'm confused as i'll have to get the portal to look for 2 related tables? how do i do this?