If this is making you struggle, then you should be going back to the fundamentals of C# first with variables and types. Declaring a ListBox dynamically won't do anything unless you add it to the form container and you assign it's other properties to define a placement and all of that... Why aren't you using the Designer view for this? I don't understand. :S

But if this confuses you, I really think it would be helpful and beneficial to your understanding if you just backtrack a little and learn about the Designer and adding/managing controls.

Frequencies, assuming it's a ListBox , looks like it's already on the form, so you shouldn't have to declare a new instance of the ListBox anyways... It's already on your Form.