Entry with a stringformat

I have an entry view set up with a stringformat so that I can show a decimal filed as 1.50 instead of it showing as 1.5. For example:

        <Entry x:Name="txtExtraLabor"
                Grid.Row="2" Grid.Column="1"
                TextColor="Black"
                Keyboard="Numeric"
                Text ="{Binding EXTRALABOR, Mode=TwoWay, StringFormat='{0:0.00}'}" />

Works great except when I go to update the value in the entry view. I can't backspace through the value. Is there a better way of formatting how the value displays in an entry view?