You can do this buy using javascript;
Here is the code for generating dynamic textbox
function abc(){
var myTable=document.getElementById('myTable');
var lastRow=myTable.rows.length;
var val='';
var rows = myTable.getElementsByTagName('tr');
var cels = rows[lastRow-1].getElementsByTagName('td');
var row = myTable.insertRow(lastRow);
var cell = row.insertCell(0);
var el = document.createElement('input');
el.setAttribute('type', 'text');
el.setAttribute('name','addte');
val='d'+lastRow;
el.setAttribute('id','d'+lastRow);
cell.appendChild(el);
}
similarly add lines to this function to generate dynamic checkbox.
Call this function on the click event on the item of the pull down menu.
Cheers,
SP

http://www.videoediting-direct.co.uk