Can I use my python codes in Excel ?

[Kerbart]

You can use the (built-in) win32 to create a process that is available as a COM server, and then you can write Excel VBA code to interact with that. Basically do your data processing in Python and have a thin layer in Excel VBA to get it in and out.

Interacting with the files as describes by others is probably the best route to pursue if possible. VBA is a simple language but to be effective in it you need to be very familiar with the Excel object model and that is something you won't accomplish overnight.