Caustics are light, so increasing or decreasing the emitter's intensity which is producing the caustics in Multilight should work. If you don't want the caustics at all, you can disable Reflected or Refracted caustics (direct or indirect ones) in Render Options > Global tab > Illumination and Caustics (in Studio) or in Render Setup > Renderer tab > Render Layers (in 3ds Max).
Also, in the case the caustics are reflected, you can tweak the material's reflective layer or BSDF to make it more or less reflective, so the light will bounce more or less. In the case the caustics are caused by refractions, you can tweak the transmittance and attenuation distance of the material that causes the caustics to make it more or less transparent so the caustics will show more or less accordingly.
I hope this helps.