Should be simple, but I haven't figured it out:

Lets say I have a contacts folder with a custom form called
'Soccerteam', with 10 contacts created using this form.

Now I want to add a text field to this form called 'Jersey Number'. I
publish the form, and any new contacts have the 'Jersey Number' field
in them.

Heres the problem: When I open up any of the contacts created before
today, they do NOT have the 'Jersey Number' field. How can I edit these
forms so that the changes I make apply to existing items in the folder?

Would really appreciate an answer - I'm stumped and can't find any help
through microsoft help/ website so far.

Thanks!

- Rahul