For a note to work, you don't need to write anything where it says "CallbackFunc". Your problem is that you don't have </CATEGORY> to close the Journal category. Your .lang should look like this:
<LANGUAGE>
    <CATEGORY Name="CustomStoryMain">
        <Entry Name="Description">A test description.</Entry>
    </CATEGORY>
    <CATEGORY Name="Journal">
        <Entry Name="Note_Test01_Name">Important note</Entry>
        <Entry Name="Note_Test01_Text">Important note</Entry>
    </CATEGORY>
</LANGUAGE>
Btw, this should be in the Custom Stories Development Support forum.