<script type="text/javascript">
function add() {
    var num = document.getElementById("num").value;
    var ifile = '';
    for(i = 0; i < num; i++) {
        ifile += '<input type="file" name="'+i+'" size="40"><br />';
    }
    document.getElementById("files").innerHTML = ifile;
}
</script>

[HTML] pobierz, plaintext 
<div id="files">
</div><br />
<input id="num" type="text" />
<button onclick="add()">dodaj</button>
[HTML] pobierz, plaintext