<script language="javascript">

function check_Only(cb)

{
    for (j = 0; j < 7; j++)

    { 
        if (eval("document.myform1.my[" + j + "].checked") == true)

        {
           document.myform1.my[j].checked = false;
           if (j == cb)

           {
              document.myform1.my[j].checked = true;
           }
         }
    }
}

</script>