อยากจะกำหนดค่าของ checkbox ที่ส่งโดย javascript (ajax)

	   var HttPRequest = false;

	   function doCallAjax(Mode) {
		  HttPRequest = false;
		  if (window.XMLHttpRequest) { // Mozilla, Safari,...
			 HttPRequest = new XMLHttpRequest();
			 if (HttPRequest.overrideMimeType) {
				HttPRequest.overrideMimeType('text/html');
			 }
		  } else if (window.ActiveXObject) { // IE
			 try {
				HttPRequest = new ActiveXObject("Msxml2.XMLHTTP");
			 } catch (e) {
				try {
				   HttPRequest = new ActiveXObject("Microsoft.XMLHTTP");
				} catch (e) {}
			 }
		  } 
		  
		  if (!HttPRequest) {
			 alert('Cannot create XMLHTTP instance');
			 return false;
		  }
	
		  var url = 'tab_add.php';
		  var pmeters = "&tArtist=" + encodeURI( document.getElementById("txtArtist").value ) +
						"&tTitle=" + encodeURI( document.getElementById("txtTitle").value ) +
						"&tFile=" + encodeURI( document.getElementById("txtFile").value ) +
						"&tRgt=" + encodeURI( document.getElementById("chkRgt").checked ) +
						"&tLgt=" + encodeURI( document.getElementById("chkLgt").checked ) +
						"&tBass=" + encodeURI( document.getElementById("chkBass").checked ) +
						"&tPer=" + encodeURI( document.getElementById("chkPer").checked ) +
						"&tVocal=" + encodeURI( document.getElementById("chkVocal").checked ) +
						"&tKb=" + encodeURI( document.getElementById("chkKb").checked ) +
						"&tMode=" + Mode;

			HttPRequest.open('POST',url,true);

			HttPRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
			HttPRequest.setRequestHeader("Content-length", pmeters.length);
			HttPRequest.setRequestHeader("Connection", "close");
			HttPRequest.send(pmeters);
			
			
			HttPRequest.onreadystatechange = function()
			{

				 if(HttPRequest.readyState == 3)  // Loading Request
				  {
				   document.getElementById("tab_add_span").innerHTML = "Now is Loading...";
				  }

				 if(HttPRequest.readyState == 4) // Return Request
				  {
				   document.getElementById("tab_add_span").innerHTML = HttPRequest.responseText;
				   document.getElementById("txtArtist").value = '';
				   document.getElementById("txtTitle").value = '';
				   document.getElementById("txtFile").value = '';
				   document.getElementById("chkRgt").checked = '';
				   document.getElementById("chkLgt").checked = '';
				   document.getElementById("chkBass").checked = '';
				   document.getElementById("chkPer").checked = '';
				   document.getElementById("chkVocal").checked = '';
				   document.getElementById("chkKb").checked = '';
				  }
				
			}

	   }

if($strMode == "ADD")
{
	$strSQL = "INSERT INTO tt_tabs ";
	$strSQL .="(artist,title,file,ins_rgt,ins_lgt,ins_bass,ins_per,ins_vocal,ins_key) ";
	$strSQL .="VALUES ";
	$strSQL .="('".$_POST["tArtist"]."','".$_POST["tTitle"]."','".$_POST["tFile"]."','".$_POST["tRgt"]."','".$_POST["tLgt"]."' ";
	$strSQL .=",'".$_POST["tBass"]."','".$_POST["tPer"]."','".$_POST["tVocal"]."','".$_POST["tKb"]."') ";
	$objQuery = mysql_query($strSQL);
}