c# - Modify Existing HTML Table -

i have html table request webserver in c#. displaying page in aspx webform. how can add prerequisite based on course id last column in table without hard-coding prerequisite? example of table design below.

<tr bgcolor="#e1e1cc">    <td width="7%">003597</td>    <td width="5%">01</td>    <td width="1%">opt</td>    <td width="8%">mt h   </td>    <td width="16%">2:00 pm - 2:50 pm  </td>    <td width="17%">08/26/13 - 12/12/13</td>    <td width="8%">        <a href="http://www.mnsu.edu/registrar/building.html"target = _blank>            <b>tr c124</b>        </a>    </td>    <td width="19%">staff</td>    <td width="4%">22</td>    <td width="4%">6</td>    <td width="4%"><font color="#000000">open</font></td>    <td width="7%">         <a href=notes.asp?spclnote=20143+003597+it+100 target = _blank>            <b>notes</b>         </a>    </td> </tr>  <tr bgcolor="#e1e1cc">     <td colspan="3">&nbsp;</td>     <td width="8%">m      </td>     <td width="16%">10:00 - 11:50 am</td>     <td width="17%">08/26/13 - 12/09/13</td>     <td width="8%">         <a href="http://www.mnsu.edu/registrar/building.html"target = _blank>             <b>wh 0119       </b>         </a>     </td>     <td width="19%">staff</td>     <td colspan="4">&nbsp;</td> </tr> 

if getting page html string insert html it. like:

private void setvalue(string pagehtml, string id, string texttoinsert) {     string html = pagehtml;     string smyhtmltoinsert = texttoinsert;     int isplitindex = html.indexof(id);     isplitindex = html.indexof("{tag}",isplitindex);     string shtml1 = html.substring(0, isplitindex);     string shtml2 = html.substring(isplitindex);     string sfinalhtml = shtml1 + smyhtmltoinsert + shtml2; }