Background changes

I have a couple of interesting questions

1) Can we write a program that allows the user to write to the resource file? If so how?

2) If i create a program which allows the user to change the background of a form to his/her own graphic of choice (the background is actually an enlarged picture box), are there any commands where I can call the other forms in the project to automatically refresh itself so that they will also immediately change their background according to the first form?

Thank you.