c# - Get Binding from DataGridTemplateColumn

Question

I'm trying to build a generic converter to Excel for my DataGrid. I'm using WPF 4.0 and a DataGrid User Control. This converter should take all values from this grid (or selected rows of it) and export to excel (by saving a file). It works, but i'm having some trouble with DataGridTemplateColumns, because DataGridTemplateColumns doesn't accept directly binding in WPF (i use DataGridTemplateColumns to show an text and a image inside a cell, like this => [ ] "Yes" - Yes is an Text and [ ] an image, so it's one binding to TextBlock and another to Image). This is an example of a DataGrid:

<ct:DataGridExtended AutoGenerateColumns="False"
                         HorizontalAlignment="Stretch"
                         VerticalAlignment="Stretch"
                         IsReadOnly="True"
                         FrozenColumnCount="7"
                         Margin="-1,59,-1,25"
                         Grid.Column="2"
                         ScrollViewer.IsDeferredScrollingEnabled="True"
                         ct:DataGridDoubleClick.ExecuteCommand="{Binding InformacoesPeca}"
                         ItemsSource="{Binding Placas, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                         SelectedItem="{Binding PlacasSelectedItem, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                         SelectedIndex="{Binding PlacasSelectedIndex, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                         ut:SelectedItemsBehavior.SelectedItemsChangedHandler="{Binding Path=ResultsSelectionChangedCommand}">
 <DataGrid.Columns>
<DataGridTextColumn Header="Cone Seq. Orig."
                                Binding="{Binding OriginConeSeq}"
                                Visibility="Hidden" />
            <DataGridTextColumn Header="Cone"
                                Binding="{Binding Cone.ConeId}" />

<DataGridTemplateColumn Header="Nec. Acomp.">
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate>
                        <Grid>
                            <Image Source="{Binding MonitoringNeed,Converter={StaticResource YesNoInstructionImageConverter}}"
                                   Height="16"
                                   Width="16"
                                   HorizontalAlignment="Left"
                                   Margin="2,0,0,0" />
                            <TextBlock Text="{Binding MonitoringNeed,Converter={StaticResource NoEmptyStringConverter}}"
                                       HorizontalAlignment="Left"
                                       Margin="22,0,0,0" />
                        </Grid>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
            </DataGridTemplateColumn>
 </DataGrid.Columns>
</DataGridExtended>

So, i have no problem to get data from a object using Binding from a DataGridTextColumn, but i couldn't figure out how to take Binding from DataGridTemplateColumn.

I've studied a lot of examples, including some here (like this: Get textbox binding in wpf datagridtemplatecolumn) on StackOverflow and still i'm stuck.

There's another problem but this one i've resolved: I need to take only those columns who's visible to user. I resolved using the Visibility Property of DataGridColumn, then i'm trying to resolve that TemplateColumn problem by getting only the value from that cell.

I hope I have been able to explain my problem.

Thanks for any help. Gustavo.