Paul may be open for business,
I think you can just use the Open DB command and trap for an error (error capture must be on). So on Error the DB isn't open, don't attempt to do anything with the related file or you'll get the lost communication with host dialog. Just try the Open DB command again later. A Timed Script trigger attached to the opener files layout should work as the timer.
If its not open, but is available, then it will open. If it was open, went off-line, and is now available again, then it will open.
Note, if data from the related file is displayed on the current layout anything you do could bring up the "Lost Communication with Host" dialog. I suggest switching to a blank layout in the Opener file that is connected to a local table before doing anything else in the Keep Alive script.
You'll have to try this out with a file your can take off-line for testing.
You could also test for a specific open window if that will tell you what you want.
- some variation of: PatternCount ( WindowNames ( FileToTest ) ; WindowNameToTest ) ≥ 1