If you actually open a file, you update it's access time, and you interfere with the process that should actually open the file. Those both break perfectly simple business logic.
The documentation for OF_EXISTS literally says it will open then close it. I leave to your imagination whether this updates the (very poorly defined) access time or not, but for sure you "interfere" with other processes...
If you want to get the access time, why don't you just query the access time? Which is likely the only thing almost universally guaranteed not to change it...
And I'm sure VB6 has an API for that, considering that VBA had a global API for it (FileDateTime).
(Which is, btw, yet another way to one-line check if a file exists).
OF_EXISTS is just a side effect of some actual operation. It's some related info you you get along the way. You would not use that as the way to only check the file. Holy cow. Please do continue trying to spread the wisom.
If you want to get the access time, why don't you just query the access time? Which is likely the only thing almost universally guaranteed not to change it... And I'm sure VB6 has an API for that, considering that VBA had a global API for it (FileDateTime).
(Which is, btw, yet another way to one-line check if a file exists).