InfoPath Dev

I don´t think you understand me. I have one document library(My document) with many different document, it can be word documents or excel documents, that doesn´t matter. Then I have one form library with my infopath-forms, in those form I want to have links to the documents in my document library(My documents). I just want to show links to ...

But I don't know the file extension.. so I can't write ".docx". I want to get this dynamical.

No I want to open a word-document that lies in a sharepoint list from inside a infopath-form. Are you with me? But I cant´t get the filename/path to the file so that I can open it, just the title.

Hi,  I have a secondary data source that is connected to a document library. In the form I want to get the full path to the document so that I can create a hyperlink to the document directly from the form. Is this possible? //Frida