First and foremost, thanks to everybody for you comments!

I believe a little clarification regarding the "binary" format would be of use. My idea was to be able to have a binary excel template, read it using Spreadsheet::ParseExcel and feed text and variables to TT for processing and then Spreadsheet::WriteExcel to a new binary file. My idea was to plugin where TT reads and writes a text file and convert "read next line" to "read next row" and "write line" to "write row".

Although the idea of marking and escaping the binary file directly seems like a nice candidate for the Obfuscation forum... my idea is to have a template that resembles the processed file for ease of template creation.

My final solution will be to convert Excel to text including a little markup that identifies columns ends and rows ends. Since a way to have markup "outside" rows and columns will arise I will use TT markup in comments that will be converted to text putting it "before" the column marker. Then run TT on it and read through the text converting the original marks to "next column" and "next row"

Thanks again to everybody.