Update MainForm from class

I'm creating a Windows app and would like to create a class that will perform some actions in the background and be able to update elements on the mainForm.  I've created the new class and an instance of it from the MainForm but I'm not sure how I can update elements such as a Tool Strip Status of the MainForm from the class when certain events happen.  I'm pretty new to C# and Windows app development so any help would be much appreciated.  

Thanks,
Tim