Regex :: Validating Email Address (Specific Domain)

I'm Using EmailValidator for Validation:
<mx:EmailValidator id="Email_Validator"
source="{txtEmail}"
property="text" required="false"/>

And My Code is:
var isValidForm:Boolean=true;
var validatorArr:Array = new Array();
validatorArr.push(Email_Validator);
var validatorErrorArray:Array = Validator.validateAll(validatorArr);
isValidForm = validatorErrorArray.length == 0;
if(isValidForm) {
//.....
}

It is working fine. But I want domain should be "gmail.com" if some other, validation should return false.. How can I achieve this? I think Regular Expressions are useful. But I don't Know to use the same in flex?...