Assalamualikum:
Umeed hai ap saab kahiriat say hongay.
bahi jaan mujhay ap se javascripts kay hawalay say help chahiya.
kah main ek project bnana cahta hoo "Stock Management" means is main stock is information hogi to bahio maine bna to lia hai but us ma ek problem hai. bahi main coding nichay de rha hoo and is ma problem yeh hai kah maine 3 columns bnanai hai 1.Purchase, 2.Sold, 3.Stock. main yeh chahta hoo kah ma puchase ki quantity daloo or sold ki to purchase ma se sold subtract ho kar result stock ma ajai then next row ke purchase ma last stock wali value ajai yaha tak to maine kar lia hai but ek problem hai kah jab meri purchase ki value zero 0 ho jai gi to ma dubara purchase ki value kasay enter karoo ga takay new balance se counting start hoo.yeh cheez mujhay samajh nahi arahi Experts please help

Code Snippet:
<html>
<head>
<title>Stock Information</title>
<link rel="stylesheet" type="text/css" href="css/style.css"/>
<script type="text/javascript">
//------------------------------------Date---------------------------------------------
var today = new Date(); //
var dd = today.getDate(); //
var mm = today.getMonth()+1; //January is 0! //
var yyyy = today.getFullYear(); //
today = dd+'/'+mm+'/'+yyyy; //
document.write(today); //
//-------------------------------------------------------------------------------------
//----------------------------------------------------
function program(a,b,c,d,e,f)
{
var total1=a-b;
document.stock.t3.value=total1;

var jump1=document.stock.t3.value;
document.stock.t4.value=jump1;
var total2= c-d;
document.stock.t6.value=total2;

var jump2=document.stock.t6.value;
document.stock.t7.value=jump2;
var total3= e-f;
document.stock.t9.value=total3;
}
</script>
</head>
<body>
<center>
<h1 class="table">Stock Information</h1>
</center>
<table width="800" align="center" class="table1">
<tr>
<th width="260"class="table">Purchase</th>
<th width="260"class="table">Sold</th>
<th width="428"class="table">Stock</th>
</tr>
<form name="stock">
<tr align="center">
<td><input id="t1" type="text" style="width:260px;" class="input1"/></td>
<td><input id="t2" type="text" style="width:260px;" class="input1"/></td>
<td><input id="t3" type="text" style="width:260px;" class="input1" onClick="program(t1.value,t2.value)" readonly/></td>
</tr>
<tr align="center">
<td><input id="t4" type="text" style="width:260px;" class="input1" onClick="program(t1.value,t2.value,t4.value,t5.val ue)"/></td>
<td><input id="t5" type="text" style="width:260px;" class="input1"/></td>
<td><input id="t6" type="text" style="width:260px;" class="input1" onClick="program(t1.value,t2.value,t4.value,t5.val ue)" readonly/></td>
</tr>
<tr align="center">
<td><input id="t7" type="text" style="width:260px;" class="input1" onClick="program(value1.value,value2.value,t4.valu e,t5.value)"/></td>
<td><input id="t8" type="text" style="width:260px;" class="input1"/></td>
<td><input id="t9" type="text" style="width:260px;" class="input1" onClick="program(value1.value,value2.value,t4.valu e,t5.value,t7.value,t8.value)"readonly/></td>
</tr>
</form>
</table>
</body>
</html>