I'm trying to customize the request form by adding 

• one single line field containing the product serial number (visible to the customer)
• two multi-line additional fields containing other request's stuff (invisible to the customer)

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For the first field, I'd like to start a procedure to check the serial number as soon as enterer by the customer by comparing it with our products DB and eventually reject the request. Is that possible? How?

I'd also like to use such serial number as a parameter for an URI link to open the specific product page to read its characteristics. Can I put the entered value into a link that I can click to open an external page  (e.g. http:\\www.company.com\query?id=$text1 (where $text1 is a variable containing the value from the additional field).

Generally speaking I don't see additional fields as URI. I only see text, number and dates. Do URI miss or are they stored in some other configuration page?

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I'd like to configure the shape of the other two multi-line fields by enlarging them and possibly putting them in a separate pane. Are they possible?

Best regards