[Opserty]

<table class="tborder" cellpadding="$stylevar[cellpadding]" width="100%">
<thead>
    <tr><td class="tcat">    
    <a href="#top" style="float:$stylevar[right]"
        onclick="return toggle_collapse('MyELEMENT')"><img
        id="collapseimg_MyELEMENT"
        src="$stylevar[imgdir_button]/collapse_tcat$vbcollapse[collapseimg_MyELEMENT].gif"
        alt="" border="0" /></a>
    <strong>Table title</strong>
    </td></tr>
</thead>
<tbody id="collapseobj_MyELEMENT" style="$vbcollapse[collapseobj_MyELEMENT]">
    <tr><td class="alt1">First row of collapsible element</td></tr>
    <tr><td class="alt2">Second row of collapsible element</td></tr>
</tbody>
<tbody>
    <tr><td class="alt1">Another row</td></tr>
</tbody>
</table>

Copied from: [b]Collapsing <table> Rows

(Note: The differences between the "style" attribute of your "tbody" and the one in that peice of code)