// Add Custom function
// Type =myfunc(1)
// in a cell to see the result
function myfunc() {}
myfunc.prototype = new GC.Spread.CalcEngine.Functions.Function("myfunc", 0, 0, {name: "myfunc",description: "This is my first function"});
myfunc.prototype.evaluate = function (args) {
    return 100;
}
spread.addCustomFunction(new myfunc());
//spread.removeCustomFunction("myfunc");