Populate a Text field using Regex and input from another field

Populate a Text field using Regex and input from another field

Hello Everyone,
In Zoho CRM, I have a field - "Website" where I put the website of my Leads. I have another field - "Website Domain". I want Website Domain to be auto-popuate using some regex formula. The regex formula will extract domain from the input - Website. Also, the Website Domain field will not be available to be edited. I can't find a way to achieve this. Please help.