function validate_required(field,alerttxt)
{
  with (field)
  {
    if (value==null||value=="")
      {alert(alerttxt);return false}
    else {return true}
  }
}

function validate_email(field,alerttxt)
{
  with (field)
  {
    apos=value.indexOf("@")
    dotpos=value.lastIndexOf(".")
    if (apos<1||dotpos-apos<2)
      {alert(alerttxt);return false}
    else {return true}
  }
}

function validate_form(thisform)
{
  with (thisform)
  {
    if (validate_required(edtperiod,"Please select a Rental Period")==false)
      {edtperiod.focus();return false}
    if (validate_required(edtdeliverydate,"Please select a Delivery Date")==false)
      {edtdeliverydate.focus();return false}
    if (validate_required(edtdeliverytime,"Please select a Preferred Delivery Time")==false)
      {edtdeliverytime.focus();return false}
    if (validate_required(edtname,"Please enter your Full Name")==false)
      {edtname.focus();return false}
    if (validate_required(edtemail,"Please enter your Email Address")==false)
      {edtemail.focus();return false}
    if (validate_email(edtemail,"Please ensure the email address you enter is valid")==false)
      {edtemail.focus();return false}
    if (validate_required(edtaddress,"Please enter your Delivery Address")==false)
      {edtaddress.focus();return false}
    if (validate_required(edtcity,"Please enter your Suburb")==false)
      {edtcity.focus();return false}
    if (validate_required(edtcodepostal,"Please enter your Post Code")==false)
      {edtcodepostal.focus();return false}
    if (validate_required(edtphone,"Please enter your Home Phone Number")==false)
      {edtphone.focus();return false}
    if (validate_required(edtcontactmethod,"Please select a Contact Method")==false)
      {edtcontactmethod.focus();return false}
    if (validate_required(edtzone,"Please select a Delivery Zone")==false)
      {edtzone.focus();return false}
    if (validate_required(edtpayment,"Please select a Payment Method")==false)
      {edtpayment.focus();return false}
  }
}