<DataGrid x:Name="grid1" Grid.Row="2" CanUserAddRows="False"
 CanUserDeleteRows="False" FocusManager.IsFocusScope="True" 
 CanUserReorderColumns="False" AutoGenerateColumns="False"
   <DataGrid.Columns>
      <DataGridTemplateColumn Header=""  Visibility="Collapsed">
          <DataGridTemplateColumn.CellTemplate>
              <DataTemplate>
                  <ProgressBar x:Name="progress1" Maximum="100" IsTabStop="False" Minimum="0" Visibility="Hidden" 
                                 Value="{Binding Path=PercentOfComplete}" Height="16" VerticalAlignment="Center"></ProgressBar>
                  <DataTemplate.Triggers>
                      <DataTrigger Binding="{Binding Path=Prop1}" Value="UserEnumType1.Value1">
                          <Setter TargetName="progress1" Property="Visibility" Value="Visible"></Setter>
                      </DataTrigger>
                  </DataTemplate.Triggers>
              </DataTemplate>
          </DataGridTemplateColumn.CellTemplate>
      </DataGridTemplateColumn>
   </DataGrid.Columns>
</DataGrid>

<DataTrigger Binding="{Binding Path=Prop1}">
    <DataTrigger.Value>
        <local:UserEnumType1>Value1</local:UserEnumType1>
    </DataTrigger.Value>
    <Setter TargetName="progress1" Property="Visibility" Value="Visible"></Setter>
</DataTrigger>