How to access control properties on other form? (Windows Mobile)

Question

Hi, I want to change the Text of a textbox which on other form.
I have tried the code below but it doesnt work.

On Form1:
Form f2 = new Form2();
f2.TextBox1.Text = "testing";

I cant get access to the controls on Form2. Why doesnt this work?

Note: Its a windows mobile application.