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You can't, but you can use split toning to emulate this, or gradient/brush tool
When you say "emulate"
can it look believable? I have no idea how to do this, so I'm just wondering before I spend time trying to figure it out.
You can pull two different white balanced images in to PS, and mask them together there. Something like the below link, although you'll probably be using less of a luminosity mask, and more of a hand-painted mask.
If you have shot raw (or bring in Jpegs or Tiffs via Camera Raw), you can bring the files into PS as Smart Objects, use masks, and click back into the smart objects to adjust color balance as necessary. Russell Brown's "Place-a-Matic" routines can be helpful with this.
If you do a lot of this (interior real-estate type photography), I suggest you try out the beta version of Oloneo's PhotoEngine. Apart from HDR, it has a feature called "ReLight" that can make this very quick and easy.