What you might do is add the process you normally use to limit the record set to the script that runs when the file opens and add a HALT script step as the last step in the script. This would stop any other script that would normally be run when the layout opens.
Another option might be to add just 2 steps to the end of your OnOpen script:
- to change to another layout without a script trigger, and then
- return to the layout you want,
and see if that triggers the OnLayoutEnter script you wanted.