<asp:FormView ID="FormView1" runat="server" DataSourceID="ObjectDataSource1" DefaultMode="Insert" Width="100%">
  <InsertItemTemplate>
  ...
  DateP:
  <asp:TextBox ID="DatePTextBox" runat="server" Text='<%# Bind("DateP") %>' />
  ...
  </InsertItemTemplate>
</asp:FormView>