Syntax to keep adding 1 to a Variable

This is driving me nuts. I am trying to add 1 to my variable everytime it is moused over. I had the syntax correct at one point, but now I cannot for the life of me get it right.

So on frame 0 of my animation I have:

sym.setVariable("myVar", 0);//Sets Variable myVar to 0

On my mouseOver I am trying to get that value to be a ++ but my syntax is off.

I have tried this:

sym.setVariable("myVar" ++);//Adds 1 to the value of Variable myVar

Doesn't seem to work. I've tried it with a comma without quotes you name it. Wish I could find some documentation beyond this page for syntax:

http://www.adobe.com/devnet-docs/edgeanimate/api/current/index.html