You can use javascript to get this done. Instead of "Yes/No" dialog you will get "Ok/Cancel" dialog box. You will have to replace "importList url"
and "main page url"
with your actual urls.
This may not be syntactically accurate but it's a start.
<head>
<script type="text/javascript">
$(document).ready(function(){
$('input[type=submit]').click(function(){
var answer = confirm("You will be forwarded. ");
if(answer){
//your logic
document.location.href="importList url";
}else{
//your logic
document.location.href="main page url";
}
});
});
</script>
</head>
<body>
<input type="submit" value="Ok" />
</body>