PostFinance offers a solution where you can enter your billing data for around 20CHF/month. Their test platform accepts data from an Excel spreadsheet.
I'm a hobby programmer with requirements similar to yours. I played around with this a few months ago, looking for open source solutions
https://start.duckduckgo.com/lite/?q...ub.com+qr+bill
and settled on
https://github.com/claudep/swiss-qr-bill
which is written in Python. I tested it by printing a QrBill, paying it through my bank's website, and receiving the CAMT054 data. Worked fine.
I'm currently exploring using the Python pyFPDF package with swiss-qr-bill to generate single page invoices as a PDF document. The top part of the invoice is human readable, and the bottom is the QrBill. Everything would be run from a PC, or, in my case, a Raspberry Pi. The plan is to print the PDF, stuff each page in an envelope, and then wait for CAMT054 messages.
Python has open source packages that can read an Excel spreadsheet (or you could export/SaveAs your Excel data to a CSV text file, and feed that to a Python program).
I hope my reply helps and didn't make this more confusing!