Is there an actual database  file (e.g. MS Access file), or are you using an
Excel to hold your information? This is not clear from your explanation,
but I assume that there is no database file  as such?

It's also not clear why the functioning for ABC (which I assume you already
have) will be different from that for XYZ.

Is it that you don't know how to update an already existing Excel file?
Simply, you will need to open  it.

Your Application object has an Open method that will open an existing Excel
file. You can process this file in the same way you are presumably already
dealing with the file you created for ABC (i.e. add a new sheet  and put the
information into it). Then Save (not Save As) the workbook.

You have not given any idea of what your code  looks like for the ABC case,
so it's difficult to say more. Why not post the relevant parts of your
code.