I have a button in which I open a dialogbox. In this dialogbox I show a Form in which I have an embedded view. Is it possible when I double click a button that it opens the document in that dialogbox??
No, that's not possible. Dialog boxes in Notes client are modal.
You can open another dialog box from a dialog box though. There you could show a document. But, it's not the same as opening a document.
It might be better if you open the document with the Form instead showing it in a dialog box.