Broad brush overview:
1) Your PLC has to have a useable communications protocol and interface, for instance Modbus on an ethernet port, in order for anything to get access to the PLC's data.
2) Excel is accessible through Microsoft's antiquated DDE component, or through a more robust OPC server. An OPC server needs a specific licensed driver for whatever comm protocol and interface your PLC is using (for example, Modbus). I don't know if OPC servers have Profibus drivers, but they routinely have Modbus drivers.
3) Matrikon, an OPC vendor, offers not only OPC servers which fetch the data from the PLC and serve it to an OPC client, but they offer a product called Excel Reporter which is an OPC client.
Matrikon's description of its Excel Reporter reads, "Excel Reporter is an out-of-the-box solution that is easy to set up, configure and manage - get up and running in less than 5 minutes," which is very likely true; I haven't used it.
Getting an OPC server configured through DCOM and talking to the PLC tags and getting the PLC protocol running is where the real work is, whose effort shouldn't be minimized. It's quite a task.
4) I have no idea what Siemens' HMI software (WinCC ?) costs but you might look into it, because whatever its name is, it is sure to have an historian component which does what you're wanting to and it should be tailored for Siemens use.