Changing date to sort code format?

If i have a column that contains a mix of '29/09/2012' format with 22-22-22 format (date and sort code) and i want to change all the date formats to sort code format (simply changing the / to -) how can i do this in a quick process?

Find and replace does not work also.

Format the cells Number format > Custom
Type

Formula:

dd-mm-yy

Or if you require a string returned

Formula:

=IF(A2="","",TEXT(A2,"dd-mm-yy"))

Find and replace will not work because the displayed date is the serial date formatted "dd/mm/yy"
i.e.
29/09/2012 is actually 41181 so there are no "/"s to replace.

That string has worked a treat mate thanks alot