AFAIK, 'currentdir' or its equivalent has been local to each app since about Win95.
So the fact that another app refers to '..' or '\' should not make any difference to yours.
Having said that, just to be safe when my app starts I get CurrentDir and save it, then base all my file paths on that throughout the progress of the app.
This will also obviously work when you sell an app - the app will (in its first line) get the user's drive and path as currentdir, then base every future path on that.
So the fact that another app refers to '..' or '\' should not make any difference to yours.
Having said that, just to be safe when my app starts I get CurrentDir and save it, then base all my file paths on that throughout the progress of the app.
This will also obviously work when you sell an app - the app will (in its first line) get the user's drive and path as currentdir, then base every future path on that.