activeSheet.setValue(0, 0, 1);
activeSheet.setValue(0, 1, 2);
activeSheet.setValue(0, 2, 3);
spread.addCustomName("customName1","=12", 0, 0);
activeSheet.setFormula(1, 0, "customName1");

var cname = spread.getCustomName("customName1");
    if (cname instanceof GC.Spread.Sheets.NameInfo) {
        //get CustomName
        var name = cname.getName();
        //get Expression
        var expression = cname.getExpression();
        //get Expression String
        var expStr = GC.Spread.Sheets.CalcEngine.expressionToFormula(activeSheet, expression, 0, 0);
        alert("Name:" + name + ";Expression: =" + expStr);
}