Maths Problem In Update

So I have VERY simple maths in my update function which is causing me a problem:

Level ++;

Thats all it is, and because its in an Update function, its gettings called every frame. How do I only make it called Once?

At the top of the file:

var levelAdvanced = false;

In Update:

if (!levelAdvanced)
{
    levelAdvanced = true;
    ++Level;
}