Open Child Form In Background Worker

I wan to open a child form and show a progress bar located in the MDI status bar.

When I use a BackgroundWorker component throws me an error because I cannot access

to the MDI Form even when I use MethodInvoker. These are the code lines:

Form form = new Form();
form.MdiParent = this; //this line gaves me an error

And this is the error description: "The calling thread cannot access this object because a different thread owns it."