You can, but it's not simple. Look at Craig Boyd blog for the solution.

http://www.sweetpotatosoftware.com/SPSBlog/PermaLink,guid,f7644db8-b155-4d43-8216-4cfde233edb7.aspx

>With MessageBox(), you can't control the position on screen. Use a form instead. For example,
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>do form MyMessageBox with "Message"
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>Here, you have the flexibility of adding additional parameters to control the position on screen, the font, buttons that the user can press, etc.
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