I don't think you explained that too well.
There are two ways to show a form from your button click event:
Form2 f = new Form2();
f.Show();
And
Form2 f = new Form2();
f.ShowDialog();
Depending on which one you choose, how your code should work will change.
The first version opens your new form, but allows it and Form1 to continue side-by side. You can enter data in both, or press the button in Form1 again to get another copy of Form2 running at teh same time.
The second version opens your new form, but does not return control to Form1 until the user closes Form2. Form1 remains inactive and can do no more actions until this happens.
If you use the former, then you need to explain in more detail what you are trying to achieve.
If you use the later, then you need to set up a public property in Form2 to return the user's choice to Form1