Customizing the sleeping system

I want a mob to spawn when the player is sleeping. This mob does certain actions when the player is sleeping and these actions take about 15-20 seconds. From the minecraft fan wiki, I found out that the player sleeps for 101 ticks/5.05 seconds to skip the night. What I want to do is change it to 300-400 ticks. How do I do it? I am very very new to Mcreator. Thank you.