If my chameleon were outside for 3-4 days out of the week, I would not use any D3 supplements. After all, they say 1 hour of real sun is equal to 12 hours under the light. And if your lighting is measuring uv in the 3s or above, there is no need for D3...which just leads me to believe that you will not need to supplement with D3.
Perhaps someone else will comment on this too.