Defining function to return a string value

Question

I wanted to declare a function in c# and use it in order to navigate a webbrowser control
I know I can do it with this:
webbrowser1.navigate(@"my htm");
I want to do this with like :
webbrowser1.navigate(the defined function);
I should also mention that I am doing a usercontrol and the filepath must be changeable from the main form
I really appreciate some help :)