ADMX Syntax Questions

Is this the latest ADMX Syntax: Download Group Policy ADMX Syntax Reference Guide from Official Microsoft Download Center (It's from 2007.)

Additionally, I'd like to configure a policy in this way:

• Enabled: Takes a string from a textbox
• Disabled: Sets a specific value
• Not Configured: Default GPO behavior (leave value as-is)

The only way I've gotten it to work, without MMC complaining, is this but it doesn't work. Additionally, the changes don't take effect. Once the window is re-opened, it's back to "Not Configured".

  <policies>
    <policy name="Policy_OverwriteSettings" class="Machine"
      displayName="$(string.Policy_OverwriteSettings)"
      explainText="$(string.Explain_OverwriteSettings)"
      presentation="$(presentation.presentation_OverwriteSettings)"
      key="SOFTWARE\Policies\Example" valueName="mydword">
      <parentCategory ref="abc:Category" />
      <supportedOn ref="SUPPORTED_Platform_Since" />
      <disabledValue>
        <string>3</string>
      </disabledValue>
      <elements>
        <text id="policy_OverwriteSettingsValue" key="SOFTWARE\Policies\Example" valueName="mydword" required="true" />
      </elements>
    </policy>
  </policies>