Hi,
wenn ich das richtig verstanden habe mach einfach:
<form action=".." method="post" id="myform">
...
<input type="file" name="file" style="display: none;" onchange="submitMyForm()" />
...
</form>
<script type="text/javascript">
function submitMyForm() {
document.getElementById("myform").submit();
}
</script>