No, in a word.

The body has a huge resource of calcium - in the bones. Calcium and magnesium ions are both essential for the creation of nerve impulses and all sorts of really basic and important body functions
If you start taking magnesium and that level rises, your body will "leach out", from your bones, enough calcium to balance the extra magnesium in your system - so if you are taking extra magnesium, you need to take a molecular equivalent amount of calcium - to protect your bones.