Capability for Javascript Complete Message

I'm struggling with a high number of Storyline courses not marking complete in my LMS. The LMS will track the interactions of the post-test but a complete message will not flow. The same courses will track correctly and mark complete but about 10-20% do not. My LMS is stating that the course is not consistently sending the message or it is being bogged down in other completion results. Someone suggested that I execute a Javascript on the Exit button of the Results slide if the user passes the post-test that will send a separate completion message to the LMS. 

Does anyone have any experience with this and how/if I might be able to do this? 

Thank you,

Lu