How to insert a specific picture to an existing pdf using Insert Pages

I have created a plugin button which I want to call the "Insert page from another file" behaviour method when pressed. Passing in a specific image file which is stored on my local machine.

So the user pressed this button and they are immediately confronted with the following dialog.

My problem is trying to get this file from c:\Sunset.jpg and pass it into the Insert Pages Dialog.

Could anybody explain how I would go about doing this.

Thanks