I am afraid that I can't explain it clearly. So, I just give a small example. I have two excel file like

File1.xls:
head1            head2
   1                  2
   3                  4
File2.xls:
head1            head3
   5                  6
   7                  8
I want to consolidate these two files into one file like

output.xls:
head1            head2           head3
   1                    2                 
   3                    4                 
   5                                      6 
   7                                      8
Though here I give two files, actually there are many files and also many columns in each files, some are common, some are different. I want to consolidate all files in same fashion. How can I do that?