How about using GridView footer for add funcionality? This way you will have all columns in same table and you'l get around your positioning problems.
Here is an example of how your gridview should look like:
<asp:GridView ID="gvTPR" runat="server" DataSourceID="SQLTPR" AutoGenerateColumns="False" ShowFooter="True" DataKeyNames="TPRID" Width="100%" EnableModelValidation="True">
<RowStyle HorizontalAlign="Center" />
<EditRowStyle BackColor="#ccffff" />
<HeaderStyle BackColor="#013b82" ForeColor="White" />
<Columns>
<asp:TemplateField HeaderText="Entered At" SortExpression="TPREnteredAt">
<EditItemTemplate>
<asp:TextBox ID="lblEnteredAt" runat="server" Text='<%# Eval("TPREnteredAt") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("TPREnteredAt") %>'></asp:Label>
</ItemTemplate>
<ControlStyle Width="90%" />
<ItemStyle Width="24%" />
<FooterTemplate>
<asp:TextBox ID="lblEnteredAt" runat="server" Text="Will be added automatically" Width="24%" />
</FooterTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Temp" SortExpression="TPRTemp">
<EditItemTemplate>
<asp:TextBox ID="txtTemp" runat="server" Text='<%# Eval("TPRTemp") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label2" runat="server" Text='<%# Bind("TPRTemp") %>'></asp:Label>
</ItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtTemp" runat="server" Text='<%# Bind("TPRTemp")%>' Width="12%" />
</FooterTemplate>
<ControlStyle Width="90%" />
<ItemStyle Width="12%" />
</asp:TemplateField>
<asp:TemplateField HeaderText="Pulse" SortExpression="TPRPulse">
<EditItemTemplate>
<asp:TextBox ID="txtPulse" runat="server" Text='<%# Eval("TPRPulse") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label3" runat="server" Text='<%# Bind("TPRPulse") %>'></asp:Label>
</ItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtPulse" runat="server" Text='<%# Bind("TPRPulse")%>' Width="12%" />
</FooterTemplate>
<ControlStyle Width="90%" />
<ItemStyle Width="12%" />
</asp:TemplateField>
<asp:TemplateField HeaderText="Respiration" SortExpression="TPRRespiration">
<EditItemTemplate>
<asp:TextBox ID="txtRespiration" runat="server" Text='<%# Eval("TPRRespiration") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label4" runat="server" Text='<%# Bind("TPRRespiration") %>'></asp:Label>
</ItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtRespiration" runat="server" Text='<%# Bind("TPRRespiration")%>' Width="12%" />
</FooterTemplate>
<ControlStyle Width="90%" />
<ItemStyle Width="12%" />
</asp:TemplateField>
<asp:TemplateField HeaderText="PCV">
<EditItemTemplate>
<asp:TextBox ID="txtPCV" runat="server" Text='<%# Bind("TPRPCV") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label5" runat="server" Text='<%# Bind("TPRPCV") %>'></asp:Label>
</ItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtPCV" runat="server" Text='<%# Bind("TPRPCV")%>' Width="12%" />
</FooterTemplate>
<ControlStyle Width="90%" />
<ItemStyle Width="12%" />
</asp:TemplateField>
<asp:TemplateField HeaderText="TP">
<EditItemTemplate>
<asp:TextBox ID="txtTP" runat="server" Text='<%# Bind("TPRTP") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label6" runat="server" Text='<%# Bind("TPRTP") %>'></asp:Label>
</ItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtTP" runat="server" Text='<%# Bind("TPRTP")%>' Width="12%" />
</FooterTemplate>
<ControlStyle Width="90%" />
<ItemStyle Width="12%" />
</asp:TemplateField>
<asp:TemplateField>
<ItemTemplate>
<asp:Button ID="lnkbtnEdit" runat="Server" Text="Edit" CommandName="Edit"
CausesValidation="false"></asp:Button>
</ItemTemplate>
<EditItemTemplate>
<asp:Button ID="lnkbtnUpdate" runat="Server" Text="Save" CommandName="Update"
CausesValidation="true"></asp:Button><br />
<asp:LinkButton ID="lnkbtnCancel" runat="Server" Text="Cancel" CommandName="Cancel"
CausesValidation="false"></asp:LinkButton>
</EditItemTemplate>
<FooterTemplate>
<asp:LinkButton ID="lnkbtnInsert" runat="Server" Text="Save" CommandName="Insert"
CausesValidation="true"></asp:LinkButton>
</FooterTemplate>
</asp:TemplateField>
</Columns>
<EmptyDataTemplate>
No TPR records exist
</EmptyDataTemplate>
</asp:GridView>
Hope this helps!
Regards, Uros