how to create a Runtime Object of window form

When you use this you are always talking about the current instance of whatever class you are in - in your case a form. So when you call a method using this as a parameter, you pass whichever instance if currently in use.

public class MyForm : Form
   {
   ...
   public void DoSomething()
      {
      MyStaticClass.MyMethod(this);
      }
   ...
   }

MyForm mf1 = new MyForm();
MyForm mf2 = new MyForm();
mf1.DoSomething();
mf2.DoSomething();

Would pass two different instances of MyForm to the static MyMethod method.

So you already do pass multiple forms!

If you have to create the forms and then pass its object to the function then perhaps you can do this

lets say forms: FormA, FormB

Modify the function like:

acb(first, second, FormA frmA, FormB frmB)

then pass the form objects as:

FormA fa = new FormA();
FormB fb = new FormB();

acb(first, second, fa,fb);

Please provide more details so that I can suggest better ways of doing this.