Change Master Page on per theme basis

I have designed a number of sharepoint (2007) themes, half of them use one MasterPage and the other half use another.

Is it possible to switch the Master Page based on 开发者_如何转开发the Theme in use?

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The source code for this Master Page Picker may be helpful. This, combined with an understanding of the ASP.NET page/event lifecycle may be all you need.