WPF双向绑定焦点有关问题

WPF双向绑定焦点问题
请教关于DataGrid上双向绑定时，从一个textbox选到另一个textbox时，焦点会跳回原位置的问题怎么解决

DataGrid添加模版

 

<DataGridTemplateColumn Header="数量"  Width="60"  >

                            <DataGridTemplateColumn.CellTemplate>

                                <DataTemplate >

                                    <MyContrl:MyTextBox Text="{Binding FSecQty,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"

                                                        FDetailClass="{Binding ID,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" 

                                                        TextChanged="MyTextBox_TextChanged_1" />

                                </DataTemplate>

                            </DataGridTemplateColumn.CellTemplate>

                        </DataGridTemplateColumn>

  <DataGridTemplateColumn Header="重量"  Width="80"  >

                            <DataGridTemplateColumn.CellTemplate>

                                <DataTemplate >

                                    <MyContrl:MyTextBox Text="{Binding FQty,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"

                                                         FDetailClass="{Binding ID,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" 

                                                        TextChanged="MyTextBox_TextChanged_2" />