As I am sure you have come to realise, Nik Silver Efex Pro does not support control points for tonal changes. This leaves you a couple of choices:
Upgrade
If you have Photoshop, then upgrade to Photoshop version so that you can use layers.
Your workflow would then be:
- Export to Photoshop
- Run Silver Efex for first layer to tone for specific parts of image
- Select background layer and repeat
- Now use layer masks or eraser tool to blend the resulting images together
Long Workflow
You can achieve the same results as above by using separate images
Your workflow would then be:
- Export to Silver Efex and tone for specific parts of image
- Repeat above steps as required
- Now use an image manipulation tool that supports layers. This could be anything from The Gimp, Photoshop Express to Paint.NET
- And apply the masking/erasing to achieve your composite image
Not Quite Shorter Workflow
You can use the above workflow and then use perfect layers to highlight the generated images with silver effects and then use OnOne Perfect Layers to create the composite.
This allows you to stay within Lightroom to achieve your effex [pun intended]