MDI forms

Question

Please try to understand my need.

I have a project it has 3 froms.

Form1 is - MDI Parent
Form2 is - MDI Child
Form3 is - MDI child

I have already open the Form2 inside Form1(The parent form).

Form2 has a button.if clicked i want to open From3 inside the parent form(in my case it is Form1)

I already use the

Form2 form2 = new Form2();
from2.Mdiparent = this;
form2.show();

but i cant use the same code to open Form3 in the parent form(The parent form is Form1) because now i'm on the form2 so i can't use the key " this " am i correct?

please help me on this please.