Diplay of checkout-form-custom-fields (user upgrade)

Hi there,

Do you know how can I use the custom fields for logged users?

I can display them only per CSS, but they are disabled (due to JavaScript, I think).

I have a website with the option of a free registration, I don’t collect there the address, zip code, city and country, as I want them to register quickly. For those members doing an upgrade, I need the information though for the invoice. The use also has to check and accept the comercial conditions.

So how can I enable the custom fields? I appreciate any help.

Kind regards
Carlos