I mean I want to integrate with a payment gateway in my country (NL)- that I would like to add more fields in Stuff modules. When user add an entry, they have to fill 2 more fields (these fields will connect with payment gateway) - if they fill in correct, they will able to add the entry. Otherwise, they will be refused.
Good, I would personally recommend you work within the payment systems provided by the uCoz service. Modules outside of the E-Shop module may not have the required security restrictions implemented to ensure data security, and personal information, especially payment information, placed within insecure fields is a disaster waiting to happen.
Although it sounds like it would be possible, it would require a large amount of custom coding (most likely involving custom php function calls), and as I have said above, data security cannot be ensured which on today's internet isn't a necessarily safe way to conduct transactions or store user personal information.
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