"Concatenating text fields over a time period"

Hi all,
I've examples from a database with two attributes- a 'data_time' and a 'text'. I'm trying to aggregate all examples from the same day into a single example, so what I want to do is concatenate their text fields and set the Time field to the beginning of the day (actually i'd like to be more general and do it over any period, but the day will do for now!)

For example, the two examples

date_time            | text
-----------------------------------
01/16/2011 23:09:34  | "foo foo"
01/16/2011 10:05:25  | "bar bar"

would be concatenated into a single one:

date_time            | text
-----------------------------------
01/16/2011 00:00:00  | "foo foo bar bar"

I'm also turning the examples into word vectors with "Process Documents from Data", so I think I can use the Aggregate operator after that, but I can't figure out how.

Cheers!