I have a very simple histogram with a drill down dimension (or group) consisting of two fields - YearMonth and Date. The group is called "DrillDownDim". My expression is sum(sales)/count(distinct Date). This works fine. What I want to do is change the title in chart depending on the level of DrillDownDim. I would like to do something like this: "if (DrillDownDim = "YearMonth", 'This is Monthly', 'This is daily'). How can accomplish this?