Oh Sorry I did not understand the question.
While you are trying to create a New Infotype with multiple subltype ( For eg ike Infotype 0006), then also it will have the same screen no as 2000. In case you want to modify or change the behaviour of the screen based on your subtype you can do so in coding on the screen.
Check the below Link.
**************** - Creation of Custom Infotype with multiple Subtypes
Hope this helps.