Another question was asked in the newsgroups about how to get access to an SPFile object, and once that is object is harnessed, how to open the file in a binary read.
In order to go this, you should setup a new method that is taking a string parameter
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Read the complete post at http://www.sharepointsecurity.com/blog/general/how-to-open-an-spfile-to-access-content/