Perfomance with Partitioning

Hi,

I've got a table holding data dispersed over a period of 1 year....but I often just need access to the last week. Well, the first thing I thought of, was: I could improve the access performance on the last week's data perhaps by partitioning the table...

The actual question is: Is there a way of "structuring" my table in such a way that the partition holding last week's data never holds more than last week's data (->as soon as the data becomes old, it would have to move into a different partition)?
A range partition over the "date" column of the table would fullfill the first requirement (=last week's data) but, but the size of the last week-partition would grow because of new data being inserted into the same partition...
My goal is to keep the last week-partition permanently as small as possible, in order to achieve a performance gain.

Hmm, does anyone have any ideas? (Maybe it's a default issue with a standard answer :))
Thanks in advance...

Kind regards,

                        Can