Custom field text in Page / Post to show in sidebar

I need to add in the Custom field in Post or Pages some html (A Pic, with some text), so that it gets displayed in the side bar. But I have looked every where to see if I find a way to do it (so that the text in the post and the Custom field are related sort to speak).

If that page does not have a Text box ready nothing will happen on the right hand side.

Each post should have its own box with its own stuff on the right hand side. Is there a hack or plugin that does that? Please and thank you.