According to the Nyquist manual:

(eq-band signal hz gain width)
    A fixed- or variable-parameter, second-order midrange equalization (EQ) filter based on snd-biquad, snd-eqbandcv and snd-eqbandvvv. The hz parameter (a FLONUM) is the center frequency, gain (a FLONUM) is the boost (or cut) in dB, and width (a FLONUM) is the half-gain width in octaves. Alternatively, hz, gain, and width may be SOUNDs, but they must all have the same sample rate, e.g. they should all run at the control rate or at the sample rate.

As expected the following produces a 12dB cut centred around 2kHz

(setq freq 2000)
(setq amp -12)
(setq Q 2.0)
(eq-band s freq amp Q)

Replacing the number with sounds;

(setq freq (force-srate (snd-srate s) (const 2000.0)))
(setq amp (force-srate (snd-srate s) (const -12.0)))
(setq Q (force-srate (snd-srate s) (const 2.0)))
(eq-band s freq amp Q)

Unfortunately this produces an error in Audacity, although it works in the standalone version of Nyquist.

The error says "error: unbound function - SND-EQBANDVVV"
I've checked with Apropos that SND-EQBANDVVV is in Audacity, and it is.

Is there any way to get this to work?
Alternatively, any suggestions of a workaround (I am wanting to vary the parameters of Eq-band over time)

Steve