Question: I have one report which is all time updated and changed the file name. I want to know is it possible to make a formula (Except for Mecro code) to another worksheet without open this worksheet.

I am using indirect formula but it required to open worksheet.

Answer: 
You can either use a built in type such as ObservableCollection; examples [here](https://stackoverflow.com/questions/4279185/what-is-the-use-of-observablecollection-in-net) and [here](https://learn.microsoft.com/en-us/dotnet/api/system.collections.objectmodel.observablecollection-1?view=netframework-4.7.2). [MSDN](https://learn.microsoft.com/en-us/dotnet/framework/wpf/data/how-to-create-and-bind-to-an-observablecollection) page.

You could also create a new class that derives from List, and overloads the functions you wish to hook.

```
class ListWithAdd<T> : List<T>
{
    public new void Add(T item)
    {
        base.Add(item);
        DoStuff();
    }
}

```
Look into observablecollection <https://learn.microsoft.com/en-us/dotnet/api/system.collections.objectmodel.observablecollection-1?view=netframework-4.7.2>