How to combine date and time in DetailsView

I have 2 fields in a DetailsView bound to the same date field:

    <asp:DetailsView ID="DetailsView1" runat="server"
        AutoGenerateRows="False"
        DataSourceID="SqlDataSource1"
        DefaultMode="Edit"
        Height="50px"
        >
        <Fields>
            <asp:TemplateField HeaderText="Discharge Date" SortExpression="DischargeDate">
                <EditItemTemplate>
                    <asp:TextBox ID="TheDate" runat="server" MaxLength="8" Text='<%# Bind("ActualDate", "{0:dd/MM/yyyy}") %>'
                        Width="90px"></asp:TextBox>
                    <asp:TextBox ID="TheTime" runat="server" MaxLength="5" Text='<%# Bind("ActualDate", "{0:t}") %>'
                        Width="40px"></asp:TextBox>
                </EditItemTemplate>
            </asp:TemplateField>            
        </Fields>
    </asp:DetailsView>

And I have a SqlDataSource that has an update statement:

    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:bedssqlConnectionString %>"
        SelectCommand="MySelectProcedure"
        SelectCommandType="StoredProcedure"
        UpdateCommand="MyUpdateProcedure"
        UpdateCommandType="StoredProcedure">
        <SelectParameters>
            <asp:QueryStringParameter Name="TheID" QueryStringField="myid" Type="Int32" />
        </SelectParameters>
        <UpdateParameters>
            <asp:QueryStringParameter Name="theid" QueryStringField="myid" />
            <asp:Parameter Name="ActualDate" />
        </UpdateParameters>
    </asp:SqlDataSource>

I am used to ASP.NET setting the value of the update parameter for me when I click on submit. However, because I have split the DateTime into Date and Time, in this case only the time portion is passed back to the database. How can combine the "ActualDate" fields and assign them to the parameter used by the stored procedure?