For more info, check out Brads blog on dusting, feeding, etc - its FANTASTIC reading. Your dusting schedule will partly have to do with its age- from newborn to about 6 months, its much more intensive, but slows down greatly thereafter. If you go outdoor, you will also modify it much more than us indoor folks.
If you have a panther or veild we all pretty much use the same dusting schedule. Calcium without d3 at every or most feedings, calcium with d3 twice a month and the multivitamin twice a month also.
It depends
What type of chameleon? What gendre? Does it go outside (how much)? Do you use UVB light tubes? What do you feed it? What do you feed the feeders?
There is no one schedule that fits all situations. But typically a person uses calcium on all crickets (and other feeders with a similarily poor calcium to phosphorous ratio), but not on butterworms (and other feeders of similar good ratio). D3 (of that brand) once or twice a month. Vitamins once or twice a month.