VBA 5 help

I was asked to make a Sercurity login program, that would run up upon start up of the computer.
It also had to have a logbook, one that recorded fake attemps.
Then i hit a problem. Every time the computer is restarted, the logbook rewrites the data in the file.
If I use brinary, I cant read the file with out VB. If I use output, it will rewrite the book.
Help would be accepted.
Ash