Accessing component from class

Question

Hello I need some help... 

For example that I have main form called frmForm, and text box on it txtText. How can I change Text property of txtText from class clsClass.

I tried with, but it doesn't seems to be working :

class clsClass{

public void changeText(){

frmForm.txtText.Text = "Some text";

}}

It has to be non-value returning method (void);

Please help, thanks :)