[DUG] Validate data entry

[John Bird]

I have a related question - I have been wondering how to display data in a 
dataset that is not either simple integer, string or date-time.

Examples are:

dates stored as an 8 digit integer (YYYYMMDD) (want to display as 
dd-mmm-yyyy and I already have the code to format it how I want)

IRD numbers - 9 digits displayed as XXX-XXX-XXX

Bank accounts  integers displayed as XX-XXXX-XXXXXXX-XX

Credit card numbers displayed as XXXX-XXXX-XXXX-XXXX

in each case stored as integers, but how could I intercept the display on 
displaying the data and after entry to reformat them like this?
What do others do?

For displaying I am hoping the answer is not just to store them as strings, 
as I still have the issue of how I validate entry.

John