Write a script to fill in an excel sheet

I have an Excel file with a list of zip files and information about the zip files such as a description of the contents of that zip file. I want a program that fills in missing information based on a folder full of zip files. for example if a zip file is missing from the list (We use CRC32 on the WHOLE zip file to check for uniqueness), then I want to add it to the list. We have a second sheet that contains a list of the internal files from the zip files and their corresponding CRC32's, I want to fully populate this table as well. Any ZIP files already in the list should be left alone, only new items added. the program can be in GNU C, CPP or Python. It must not use Windows specific libraries i.e. if you are compiling on Windows you should use MINGW. It is probably best to specify an input excel file and an output excel file. This will also make it easier than modifying an existing Excel file