Filling up HTML control such as textbox

[Corobori]

I have got a form for data input. When the "Save" button is pressed I
am doing the Insert thing in the database and depending on some data I
have to either say "Ok, your ads is published"; or say "You need to pay
$ssss for publishing your ad".

In the situation when the user have to pay I have to submit some data
to a cgi which will be displaying some form not under my control. I
used to do it like this

<form id="Form1" method="post"
ACTION="http://www.xxxx.xx/cgi-bin/tbk_bp_pago.cgi">
<INPUT TYPE="text" NAME="TBK_TIPO_TRANSACCION" VALUE="TR_NORMAL"
ID="Text1">
<INPUT TYPE="text" NAME="TBK_AMOUNT" VALUE="1100" ID="Text2">
<INPUT TYPE="text" NAME="TBK_URL_KO" SIZE="40"
VALUE="http://www.xxxx.xx/mypagefailed.htm" ID="Text6">
<INPUT TYPE="text" NAME="TBK_URL_OK" SIZE="40"
VALUE="http://www.xxxx.xx/mypagefine.htm">
.....

In asp.net I am a bit confused. It seems I am allowed one form
"runat=server" per page.
Can I add a form without "runat=server" ? In that case how can I
dynamically fill the data such as TBK_AMOUNT ?

Any clue is welcome !

Jean-Luc
http://www.corobori.com