Napio,
To open any file only with your program, you can do one thing, but it is a bit difficult. Anyway, one of the solution which I used for a similar problem was to create a "Dll" file in VB with two functions "Encrypt" and "Decrypt" to encode and decode any file. Now initally you encrypt your file separately. When your program is run, you call the "Dll file" routine "Decrypt" to decode the file, work with it and when your program is closed you "Encrypt" it.
This will prevent your program from being accessed other than your program.
Hope this helps,
Regards.
----------------------------------------- There is always a new solution for the same problem.
Anonymous