I do almost exactly the same as Emseven, but instead of keeping oil and vinegar at work (good idea though!) I dress with butter and/or dripping. It stays solid in the lunchbox, so it doesn't leak all over the inside of my bag. Then at lunchtime I extract it onto a plate and melt it in the microwave. Then I tip the salad onto the plate with the molten fat and stir it all in.
My colleagues generally tell me it looks 'healthy' and 'tasty'.