function isDigit(c)
  {
     var test = "" + c;
     if (test == "0" || test == "1" || test == "2" || test == "3" || test ==
"4" 
     || test == "5" || test == "6" || test == "7" || test == "8" || test == "9")
    {
     return true;
    }
  return false;
  }
<!--
function isAllDigits(s)
    {
    var test = "" + s;
    for (var k = 0; k < test.length; k++)
        {
        var c = test.substring(k, k+1);
        if (isDigit(c) == false)
            {
            return false;
            }
        }
    return true;
    }

function numaOK()
 {
    var num = document.forms[ 0 ].numa.value;
      if (num.length == 9)
        {
          var result = isAllDigits(num);
           if (result == false)
            {
              alert("YOUR STUDENT NUMBER CAN ONLY CONTAIN NUMBERS (0-9)");
            }
          return result;
        }
     else
      {
        alert("*** PLEASE ENTER YOUR 9 DIGIT STUDENT NUMBER ***");
        return false;
      }
 }

function checkForm()
 {
   if (numaOK() == false)
    {
      return false;
    }
 document.forms[0].submit();
 }
//-->