Change text input value with jQuery

I'm making a newsletter contact form, and in that form the user can check the subjects they want to receive newsletters from.

I want to make a text input where its value will be the value of all the checked boxes, separated with commas.

e.g.: retails, news, manufacturing

I want it to be dynamically, when the user checks a box it appears on the text input at the same moment, and when the user uncheck the box, it desappear at the same moment too, so I think jQuery is the easiest way, I just don't know how to do it.

Any ideas?

Thank you!