//http://www.addedbytes.com/lab/select-all-javascript-for-forms-posting-to-an-array/
var formblock; 
var forminputs; 
function prepare() { 
  formblock= document.getElementById('form_id'); 
  forminputs = formblock.getElementsByTagName('input'); 
} 

function select_all(name, value) { 
  for (i = 0; i < forminputs.length; i++) { 
    // regex here to check name attribute 
    var regex = new RegExp(name, "i"); 
    if (regex.test(forminputs[i].getAttribute('name'))) { 
      if (value == '1') { 
        forminputs[i].checked = true; 
      } else { 
        forminputs[i].checked = false; 
      } 
    } 
  } 
} 

if (window.addEventListener) { 
  window.addEventListener("load", prepare, false); 
} else if (window.attachEvent) { 
  window.attachEvent("onload", prepare) 
} else if (document.getElementById) { 
  window.onload = prepare; 
}