// enables or disables the "extra" input field. Null safe.
function setExtraInputFieldEnabled(extraInputFieldEnabled, extraInputField) {
    if (extraInputField == null) {
        return;
    }

    extraInputField.disabled = !extraInputFieldEnabled;
}

// checks to see if a given value is selected in a checkbox array
function isValueChecked(field, value) {
    if (field == null) {
        return false;
    }

    for (i = 0; i < field.length; i++) {
        if (field[i].value == value && field[i].checked) {
            return true;
        }
    }
    return false;
}

// checks to see if a given value is selected in a select list
function isValueSelected(field, value) {
    if (field == null) {
        return false;
    }

    if (field.value == value) {
        return true;
    }
    return false;
}