fill a Input text in a row in a table

You could try this. (I am not sure though, not enough info)
hope it helps

assume you have a form like this 2 tables and a button

<form id="form1" runat="server">
  <div>
  </div>
  <asp:Table ID="Table1" runat="server" Height="185px" Width="341px">
  <asp:TableRow>
  <asp:TableCell ID="r1">
      <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox></asp:TableCell>
  </asp:TableRow>
  <asp:TableRow ID="r2">
  <asp:TableCell ID="txtcell">
      <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox></asp:TableCell>
  </asp:TableRow>
  </asp:Table>

<hr />


  <table id="Table2" runat="server">
  <tr>
  <td> <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox></asp:TableCell></td>
  </tr>
  <tr>
  <td> <asp:TextBox ID="TextBox4" runat="server"></asp:TextBox></asp:TableCell></td>
  </tr>
  </table>

  <br />
  <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
  </form>

put this in your code behind

protected void Button1_Click(object sender, EventArgs e)
{ TextBox txt = (TextBox)FindControlRecursive(Table1, "TextBox1");
TextBox txt2 = (TextBox)FindControlRecursive(Table1, "TextBox2");
TextBox txt3 = (TextBox)FindControlRecursive(Table2, "TextBox3");
TextBox txt4 = (TextBox)FindControlRecursive(Table2, "TextBox4");
txt.Text = "yourvalue";
txt2.Text = "yourvalue2";
txt3.Text = "yourvalue3";
txt4.Text = "yourvalue4";
}


public Control FindControlRecursive(Control Root, string Id)
{
if (Root.ID == Id)
return Root;
foreach (Control Ctl in Root.Controls)
{
Control FoundCtl = FindControlRecursive(Ctl, Id);
if (FoundCtl != null)
return FoundCtl;
}
return null;
}