Identify role using an email field in the form

Hello, I have various fields on a form. In a records I have first name, last name and email field. Through the email field I want to identify the role of the person mentioned in the record. 

I have certain dynamic rules that need to be created. So when the person identified using the email field belongs to a Role A, a section needs to be displayed on the form. How do I achieve this? 

I suppose there needs to be a code written to get the role of the person mentioned in the record through email field. Thanks.

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Raj Helaiya
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