How can I implement an if statement within a HTML form that allows a user to click 'next page' if they get a certain score

I have created a quiz within html using various functions. I would like the user to be able to click the 'next page' button, only if they achieve a certain score from the quiz. Any ideas of how I could implement this?

Below is the script I am using. It shows the calculation sum to get a score for their answers as well as a message that corresponds to their score.

The issue I am having I am not sure on how to implement some sort of script that allows the user to click the 'next page' button if they achieve a grade of 75 or above. Any help is much appreciated - a newbie to html

    <script> 
document.getElementById("form3").onsubmit=function(){

  hr = parseInt(document.querySelector('input[name = "hr"]:checked').value);
  prevent = parseInt(document.querySelector('input[name = "prevent"]:checked').value);
  hmrc = parseInt(document.querySelector('input[name = "hmrc"]:checked').value);
  email = parseInt(document.querySelector('input[name = "email"]:checked').value);
  paypal = parseInt(document.querySelector('input[name = "paypal"]:checked').value);

result = hr + prevent + hmrc + email + paypal;

document.getElementById("grade").innerHTML = result;

if (result ==  0) {result2 = "Not good enough, you could potentially become a victim of social engineering in the future."};
if (result ==  25) {result2 = "You need to spend more time. try again."};
if (result ==  50) {result2 = "You could do better, try again."};
if (result == 75) {result2 = "Pretty good job."};
if (result == 100) {result2 = "Great Stuff! You clearly understand the dangers of social engineering! "};
document.getElementById("grade2").innerHTML = result2;



return false; 
} 

</script>