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I need to gather some more information from you in order to help....the 650 is programmed using your computer/laptop. Is that how you are trying to find the correct controller of volume?Let me know.
Ok, I'm only familiar with Logitech's desktop software. You can download it for free and I think you will find that it has a lot more options. You can download it HERE.
Give it a try. It definitely will give you that option.
For the software? No it should be free.