Heeelp! I cannot save to excel and display to crystal report...very hard obstacle..stuck!!

Question

  Heeelp! I am stuck heavily!! I have this big obstacle that it seems impossible to resolve and it also seems there is no solution behind it!! It may seem easy at first glance but it is the most challenging obstacle in programming history. How can I save a file in excel, display it in crystal report, close the crystal report and save the file again? I know this may seem to be a beginners question but it is in fact an advanced question. The reason is, because when you save a file in excel using C# and display it in the crystal report, you cannot save the file again..because the file is in use and no matter what you do to close the file you cannot close the file...it is impossible to achieve...or at least it is impossible for me. Plese anyone can help me it would be greatly appreciate it. I have the entire project WITH source code attached here to try it out yourself. See what I mean?