Checking The Validity Of The Email?

1. I have a javascript with which I am checking the validity of the email provided:

function checkEmail($email)
{
if(eregi("^[a-zA-Z0-9_]+@[a-zA-Z0-9-]+.[a-zA-Z0-9-.]+$]", $email)) [code]...

2. Later I have another javascript which check the input field and changes the color if condition not met.

function validateForm (){

var value1 = document.getElementById('field1');

if(value1.value == "Fill in the Name") {value1.style.color = '#ff0000';} red letters IF NOT CHANGED

3. I want to include the above mentioned email function into this function as well.For example to do something like the following

if(value1.value == "" || checkEmail($email) != TRUE) {value1.style.color = '#ff0000';} red letters

Can I use information from another validation script (first script) or I need to include it inside the ValidateForm script (second script) as well?