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The simple answer is to tell you to change your F specs to “F”ull procedural and just code the I/O logic in your calc specs.
That being said, do you have any access to source code that uses this technique or do you have any experience with this type of processing?
If not, you really should take a class or purchase a book or two.
Once you get started on your project, and have specific questions, please come back and ask them.