Required Field Validator Control

I have a question concerning the required field validator control. I have a form where I am using this control to validate that the user has inputed at leat something in the field. But I was wondering if I could use the same control for my own function that I want to use to do further validation once the user has inputed some data. For example in the case of providing an inoput field for email address. First Im test to see if they entered a valid value. Then I use a fuction I wrote to make sure the data is a valid email address. Thanks In Advance.
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