For starters Calcium isn't particularly absorbable and like most things how it got in your body, be it through food, supplements and in what form is an important factor. Calcium is constantly being turned over by bone intestines nad renal system.
The transport of calcium itself is controlled by three hormones, parathyroid hormone, calcitonin and a metabolite of vitamin D called 1,25 dihydroxyvitamin D which is basically why you need vitamin D in Calcium synthesis and general homeostatis.
When you ingest some Calcium be it a present in a some milk or if you eat a piece if chalk, the Vitamin D metabolite governs the rate of absorption from the intestines.
As a general rule, in food form, and possibly without some hi-tech supplement if you ingest about 1000mg of calcium a day, you will absorb about 350mg from intestine to extracellular fluid. Then part of this (about 150-200mg) is lost back through enteric secretion into the gut. Your total absoroption of calcium is therefore as little as 150mg from that whole 1000mg you ingested.
In normal circadian calcium homeostatis (i.e. what happens with calcium in a day) about 500-600mg is exchanged between bone (the principle storage point for calcium) and bodily fluids. The total bone 'resevoir' of calicum is about 500 to 1500 mg with about 1000mg on average in adults.
When you are growing up, particularly in young children and during puberty absorption is higher than the figures I offerd above. Similarly those with defficiencies when suddenly taking in more calcium will have higher absoroption levels. One thing is for sure, you need Vitamin D to absorb Calcium.
My main point is its quite hard to overdose on Calcium and there are regulatory mechanisms governing absorption. The initial indicators of calcium levels being too high are constipation.
As far as Vitamin D goes, besides being involved in Calcium turnover it is also stimulates phosphate and magnesium aborption from the intestine. In Magnesium the vitamin Pyridoxine (B6) is also required for absorption.
Depending on your exposure to sunlight and skin type, cholecalciferol (type Vit D) will be manufactured by the skin when it is exposed to sunshine. Its unlikely to cause an overdose with excessive sunlight, and the same goes for dietary amounts even if you are eating calcium rich foods. I would not take a direct Vit D supplement.
Vit D overdose initially causes vomiting, nausea and a metallic taste in the mouth and also fatigue. Recorded cases of vit D overdose stem from supplements and not from foodstuffs as there is regulation to absorption as in Calcium.