Is there anyway to change themes using a program?

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http://askubuntu.com – This also means that the program can install themes by itself, because the main reason I don't want to change from the default theme is that I have to install the theme myself after downloading it EDIT: I want to be able to install theme using any theme manager (if there are any), but I don't want something where I'd have to install the theme myself and the theme manager would only change the thme (HowTos)