I don’t remember for WaveLab 8, but this is indirectly possible in WaveLab 10.
Indeed, it is possible to execute to run an ActiveX script that executes a WaveLab JavaScript. Therefore, if you create an ActiveX script that processes all files of a folder, this is what you are looking for.
BUT, I must say this was never tested, therefore I can’t guarantee it works.
To check if it is possible with WaveLab 8, check the WaveLab documentation for the ActiveX class “InnerScript”.