function ComputeAmountVat() รันแล้วเลขไม่คำนวนเลยค่ะไมทราบว่าผิดพลาดตรงไหนรบกวนช่วยดูหน่อย

function ComputeAmountVat(){	
	var AmountVat = 0;
	var SumTotalAmountVal = 0;
	var TotalDiscount = 0;

	//var TotalNetAmount = document.getElementById('TotalNetAmount');
	//var PVat = document.getElementById('PVat');
	//var PDisCount = document.getElementById('PDisCount');
	var VatType = document.getElementById('VatType').value;

	var TotalNetAmountVal = eval(TotalNetAmount.value);
	if(TotalNetAmount.value == ""){
		TotalNetAmountVal = 0;
		}
		
	var PVatVal = eval(PVat.value);
	if(PVat.value == ""){
		PVatVal = 0;
		}
		
	var PDisCountVal = eval(PDisCount.value);
	if(PDisCount.value == ""){
		PDisCountVal = 0;
		}
   
	TotalDiscount = TotalNetAmountVal * PDisCountVal/100;
	TotalNetAmountVal = TotalNetAmountVal - TotalDiscount;	
	
     var selVatType = document.form1.VatType;
	if(selVatType.options[selVatType.selectedIndex].value == "No Vat"){
		AmountVat = 0;
		TotalNetAmountVal = FormatNumber(TotalAmountVal.value , 2);
		SumTotalAmountVal = FormatNumber(TotalAmountVal.value , 2);
		//SumTotalAmountVal = TotalNetAmountVal ;
			
	}
		if(selVatType.options[selVatType.selectedIndex].value == "Include Vat"){
		AmountVat = TotalNetAmountVal * PVatVal/107;
		//AmountVat = 2+2;
	    AmountVat = FormatNumber(AmountVat , 2);
		//SumTotalAmountVal = eval(TotalNetAmountVal) -  eval(AmountVat);
		TotalNetAmountVal = SumTotalAmountVal + parseFloat(AmountVat);
		SumTotalAmountVal = parseFloat(TotalNetAmountVal);
		//document.form1.TotalNetAmount.value = FormatNumber(TotalNetAmountVal , 2);
	}
	/*if(VatType == "Include Vat"){
		AmountVat = TotalNetAmountVal * PVatVal/107;
		AmountVat = FormatNumber(AmountVat , 2);
		SumTotalAmountVal = eval(TotalNetAmountVal) -  eval(AmountVat);
	}*/
	if(selVatType.options[selVatType.selectedIndex].value == "Exclude Vat"){
		AmountVat = TotalNetAmountVal * PVatVal/100;
		AmountVat = FormatNumber(AmountVat , 2);
		TotalNetAmountVal = FormatNumber(TotalAmountVal.value , 2);
		SumTotalAmountVal = parseFloat(TotalNetAmountVal) +  parseFloat(AmountVat);
		
	}

	if(TotalDiscount == 0){
		document.form1.TotalDiscount.value = "";
	}else{
		document.form1.TotalDiscount.value = FormatNumber(TotalDiscount , 2);
		//document.form1.AmountVat.value = AmountVat;
	}	

	if(AmountVat == 0){
		document.form1.AmountVat.value = "";
	}else{
		document.form1.AmountVat.value = FormatNumber(AmountVat , 2);
		//document.form1.AmountVat.value = AmountVat;
	}	
	
	if(SumTotalAmountVal == 0){
		document.form1.SumTotalAmount.value = "";
	}else{
		document.form1.SumTotalAmount.value = FormatNumber(SumTotalAmountVal , 2);
	}
	
	document.form1.Tp_TotalQtyStock.value = document.form1.TotalQtyStock.value;
	document.form1.Tp_TotalQtySell.value = document.form1.TotalQtySell.value;
	document.form1.Tp_TotalNetAmount.value = document.form1.TotalNetAmount.value;
	
	//ComputeAmountVat();
}