invoke event from diffrent class hierarchy

[C# Programming]

Hi
I would like to update the GUI once specific scenario occurs
I’ve application that have GUI and logic layers

At logic layers I have hierarchy classes witch means that class ‘A’ use class ‘B’ that use class ‘C’, etc

At Class ‘C’ I would like to notify GUI (such as update counter edit box) once a condition exist (for example
if ((m_num % 100) == 0))
UpdateGUI(m_num)

I know I can use the event mechanism

Create and register event at class A,B,C and register also the event at the GUI

Is there any other way to call event from very low class to very higher class hierarchy?

I hope I describe my question properly

Thanks
Ronen