Hi,
I've just did a little bit of testing, I'm using Access 2000 but I've just imported an excel file that has dates in the format you specified for example:
21 August 2012
02 September 2012
11 October 2012
when I imported the excel file as a new table I then went into the design view and changed the Data Type from Text to Date/Time format, saved the table and then open up the table and the above dates displayed as:
21/08/2012
02/09/2012
11/10/2012
I know it's a manual process, but no coding required.
Alternatively if your excel file retains it's file name each time it is updated you could link to that excel file and then have a table within your database that you append this data to, and on appending to your table that has the date field already of Date/Time Data Type, your dates will automatically on being appending take the desired format.
Clearly these may not be considered to be the best method of achieving what you want and the experts may come up with something you may consider more suitable.
Just something to consider using untill you can come up with a better solution.
Regards
John