How to use a different gtk (gtk3) theme for some applications?

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http://askubuntu.com – I want to use a custom theme for Nautilus and for some other applications but i want to keep the generic theme for the rest of the applications and system. I know it can be done in gtk2. For example the theme I'm using uses a dark theme for the terminal and the image viewer and the rest of application still looks clear. Is there a simple way to do it, like setting a path to a existing theme for each application i want to customize? I hope you know what I mean, my english isn't that good. THanks. (HowTos)