HI, how to use indent in thread index page???

Hi, all:
   Currently, I want to use indent in thread index page, but it can't work,
it display two levels, one for thread root, and another for others messages
of the thread.

    what I want is to get several indent like following:

Thread Root Msg
     Msg One
          Msg Two
     Msg Three
     Msg  Four
          Msg Five
              Msg Six

The resource setting in my resource file is :

<TLEVELS>
4
</TLEVELS>

##....

<THead>
<ul class="mlist">
</THead>



<TTOPBEGIN>
<p>
<li class="thread_root"><a $A_NAME$></a><a
$A_HREF$><strong>$SUBJECTNA$</strong></a> $FROMNAME$
</TTOPBEGIN>

<TSUBLISTBEG>
<ul>
</TSUBLISTBEG>

<TLiTxt>
<li class="thread_sublist">$SUBJECT$ <em>$FROMNAME$</em>
</TLiTxt>

<TLiEnd>
</li>
</TLiEnd>

<TLINONE>
</TLINONE>

<TLINONEEND>
</TLINONEEND>

<TSUBJECTBEG>

</TSUBJECTBEG>

<TSUBJECTEND>

</TSUBJECTEND>

<TSUBLISTEND>
</ul>
</TSUBLISTEND>


<TTOPEND>
</li>
</p>
</TTOPEND>


<TSINGLETXT>
<li class="thread_root"><a $A_NAME$></a><a
$A_HREF$><strong>$SUBJECTNA$</strong></a> $FROMNAME$
</li>
</TSINGLETXT>


<TFoot>
</ul>
</TFoot>

<TIndentBegin>
<ul>
</TIndentBegin>

<TIndentEnd>
</ul>
</TIndentEnd>