<!DOCTYPE html>
<html>
<body>
<h3>A demonstration of how to access a File Upload Button</h3>
<input type="file" id="myFile">
<p>Click the "Try it" button to disable the file upload button.</p>
<button onclick="myFunction()">Try it</button>
<script>
function myFunction() {
var x = document.getElementById("myFile");
x.disabled = true;
}
</script>
</body>
</html>