Using Nik Software Silver Efex Pro 2 and Lighroom 4
How do I tone different areas of photo in beige, dark, lighter shades of grey and black and mustard shades.
by Linus Kleen
This is not a straightforward workflow for split-toning, but if you want to get some very delicate split toning in Silver Efex, try under "Finishing Details" changing the Paper Tone and Silver Tone.
As @Francesco said, there is a perfectly good split toning adjustment in Lightroom proper.
In lightroom (both 3 and 4) you have the Split Tone feature in the develop module, which allows you to choose hue and saturation both for highlights and shadows (and to decide where each one of them begins).
Here it is a quick example, where I simply converted to B&W and applied the parameters shown. The shot was hand-held :-)