string manimpulation/validation + javascript

[wxdqz]

I am lost on this. Please help. I want to validate the text field ("manemail") has "viropharma.com" at the end. If not, an alert will pop up.
I know I have this code using "substring" wrong. Please help.

checkEmail = form.manemail.value

if ((checkEmail.substring('xyz.com') =0)
{alert("Need xyz.com");
form.manemail.select();
return false;
}

Thanks!