You need to do that on the client side using javascript ( preferably ). The post data will be submitted when the form is submitted. Try adding this function as your form's onsubmit event
function func(){
var a = document.getElementsByName('removeException'),
b = document.getElementsByName('submitDate');
if(a[0].value!=null && b[0].value!=null){
var c = confirm('Are you sure you want to submit both values at the same time?')
if(c){
return true;
}else{
return false;
}
}
}
Then
<form name="dates" action="process.php" method="POST" onSubmit='return func()'>