function isFieldNumeric(sField)
{
    if (isNaN(sField.value))
    {
        alert("Error: Field must be numeric.") ;
        sField.focus() ;
        return true ;
    }
    else
        return false ;
}

function isFieldBlank(sField)
{
    if (sField.value.length == 0)
    {
        alert("Please fill in all * (required) fields.") ;
        sField.focus() ;
        return true ;
    }
    else
        return false ;
}

function isFieldUnchosen(sField)
{
    if (sField.value.indexOf("*") == 0)
    {
        alert("Please select a " + sField.value.substr(2) + ".") ;
        sField.focus() ;
        return true ;
    }
    else
        return false ;
}

function isFieldLengthWrongSize(sField, nRequiredLength)
{
    if (sField.value.length != nRequiredLength)
    {
        alert(sField.name + " must be exactly " + nRequiredLength + " characters long.") ;
        sField.focus() ;
        return true ;
    }
    else
        return false ;
}

function isFieldDateInPast(sField)
{
    var travelDate = new Date() ;
    var today = new Date() ;

    travelDate.setMonth(document.EnterInfo.travel_date_m.value - 1) ;
    travelDate.setDate(document.EnterInfo.travel_date_d.value) ;
    travelDate.setFullYear(document.EnterInfo.travel_date_y.value) ;

    if (travelDate <= today)
    {
        alert("Please specify future travel date.") ;
        sField.focus() ;
        return true ;
    }
    else
        return false ;
}

function isFieldInvalidEmailAddress(sField)
{
    var apos = sField.value.indexOf("@") ;
    var dotpos = sField.value.lastIndexOf(".") ;

    if ((apos < 1) || (dotpos - apos < 2) || (dotpos == strlen(sField)))
    {
        alert("Invalid Internet email address.") ;
        sField.focus() ;
        return true ;
    }
    else
        return false ;
}