compare two address mail

compare two address mail

Hello,
 
compare two address is this way:
 
if (input.Email_1 != input.Email_2)
{
alert "Invalid Email";
cancel submit;
}
but lot of people copy the first to fill the second...so the first is false, the second is false.
Is it possible to forbid copy in a field and write again in the second for make a  real comparison.
 
Thanks for help.
jean-marc