Registration Field unmodificable from user

Hi,
I'd like to know if there is a system to avoid user can modify some field of registration form.

For example, I create a new account and I insert all data requested, more I should insert some product data I've bought from shop (ex. serial number and date of buy).

I can modify everything, in the future, but serial number and date of my product... and I can insert any number of product I want.

Is possible? is there something can help me?

Just make the fields read only - this way you can only modify them from backend.

But this is possible only if I put this field into registration form. If I'd like to insert it after, and as administrator I've put it only read from user, I cannot enter it, as user.

lucablue wrote: But this is possible only if I put this field into registration form. If I'd like to insert it after, and as administrator I've put it only read from user, I cannot enter it, as user.

Its either read only or not.

If you want it read only, it means that your users cannot modify it.

You would need to modify it as admin from backend.