function get_invoice(){
	var ajaxRequest;  // The variable that makes Ajax possible!
	
	try{
		// Opera 8.0+, Firefox, Safari
		ajaxRequest = new XMLHttpRequest();
	} catch (e){
		// Internet Explorer Browsers
		try{
			ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e) {
			try{
				ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (e){
				// Something went wrong
				alert("Your browser broke!");
				return false;
			}
		}
	}
	// Create a function that will receive data sent from the server
	ajaxRequest.onreadystatechange = function(){
		
		if(ajaxRequest.readyState != 4){
			var ajaxDisplay = document.getElementById('checkstatus');
			ajaxDisplay.innerHTML = "<img src=/img/spinner.gif width=16 height=16>";
			
		}		
		if(ajaxRequest.readyState == 4){
			var ajaxDisplay = document.getElementById('checkstatus');
			ajaxDisplay.innerHTML = "<img src=/img/checkbullet.gif width=16 height=16>";
		
			
			
			var ajaxDisplay3 = document.getElementById('showresult');
		    var matchresult = ajaxRequest.responseText.match("go.gif");
				if(matchresult == "go.gif") {
					ajaxDisplay3.innerHTML = ajaxRequest.responseText;
				} else {
					var ajaxDisplay2 = document.getElementById('mailaddress').style.backgroundColor = '#ffcccc';
				}			
		
		}
	}
	var invoicenr = document.getElementById('invoicenr').value;
	var queryString = "?invoicenr=" + invoicenr;
	ajaxRequest.open("GET", "_amountcalc.php" + queryString, true);
	ajaxRequest.send(null); 
}