The solution all depends on how the date is currently formatted. It sounds like it is there as text and I am assuming that 1st February 2009 would be shown as 01 02 2009.
That being the case, you will have to re-assemble the pieces to make a date that Excel recognises and then you can use normal Excel formatting to get it to display however you want.
The way I would do this is to put a formula into an empty column which looked something like this:
=Date(Right(Trim(Nx),4), Mid(Trim(Nx),4,2), Left(Trim(Nx),2))
where Nx is the location of your data (N being the column and x being the row). The Trim function is used to remove any unwanted spaces that are there but you cannot see and might otherwise much this up.
Now you should have a date and you can format the cell (or whole column) using the Format function and choosing the Number tab - there are some defaults available for Date, but if you cannot find the one you want then choose Custom and type in dd-mmm-yy.
Now you can shuffle your columns around and hide the original.
Hope this all helps.
Thanks,
Caspar