Linking text boxes for automatic text update

Hello everyone!

I was wondering if there is any way of linking two o more text boxes so that when you write text in one of them it automatically changes in the other. I am not talking about threading for text overflow. I am also interested in doing the same with images.

I am going to set a practical example: a have 50 posters that are meant to be almost the same, but they all have different logos. The text and background image is the same for all of them. I would like to change the text and image in one of them, and then InDesign would automatically update the rest.

Is this possible? Any ideas?