Silverlight provides element to element binding. How to apply it this is case:

I have a xaml as below:

<TextBlock Text="{Binding ABC}" >
  <ToolTipService.ToolTip>
    <local:MyControl Title="{Binding ...}" />
  </ToolTipService.ToolTip>
</TextBlock>

I want to bind MyControl Title to the same data as its parent Textblock Text, but I don't want set x:Name for its parent Textblock.

I know there is one solution to bind Title to same data source:

<local:MyControl Title="{Binding ABC}" />

This may cause two times to call "{Binding ABC}", with my case, there ValurConverter for this binding. I don't want to use this way.