Put a oscillator ( speed key OSC ) between button press and the volume input arguments ( you will need 2 symbols, one for volume up and a second for volume down). I like to use .3s for each parameter but you can adjust the time the signal is high and low to suit your taste for ramping speed and the requirements of the unit under control. Or teach the client to repeatedly press and release the volume buttons. It is not inherently a flaw in the macro. The macro works. You wish it to work differently, So code the system, including the macro, to work as you desire by adding the oscillator symbol to the code.

Or you can become even more creative and use a press and hold macro, with the press going directly to the volume driver and the held argument going to the oscillator. You'll have to deal with jammed digital signals but an OR gate makes this rather trivial bit of code.

Or hire someone to do all of this for you.

Alan