function isValidNumber(thisField) {
    for (var i = 0; i < thisField.value.length; i++) {
        var ch = thisField.value.substring(i, i + 1);
        if (!( (ch >= "0" && ch <= "9") ) ) {
			alert("Only Numbers are allowed.");
			thisField.value="";
			thisField.focus();
        }
    }
}




/*onBlur="isValidNumber(this)"*/