From what I have read, no. Some say that calcium interferes with the absorption of magnesium, but that doesn't seem to be the case, I should say, unless there is a severe magnesium deficiency or a high calcium toxicity or excess. Actually, it seems that calcium needs magnesium for proper absorption, but magnesium is absorbed just fine on its own. The most important factor when it comes to magnesium absorption is form. Oxide is very poorly absorbed, but it is the most commonly used form in supplements. Citrate, malate, taurate, sulfate,and glycinate, and a few others are much better. Oxide has a high elemental content, but only about 4% of this form is absorbed by the body, so its content can be deceptive.
BTW, I found the link to natural eye health. I use it in conjuction with the other link I posted. I hope they help you, too.