Can I pass dynamic value to a record summry page

Are you Storing it anywhere? If yes Take a rule input for Summary Interface and pass value from Record Object 

And i got one more suggestion why don't you shift to  Events ? 

Do you mean your milestone keeps changing for different summary pages? Is it something that changes based on a csse type or some attribute?

Hm ... in my mind, a record knows its milestone and I do not need to pass it somehow.

I'm really unsure why you would want to do this but perhaps you are looking for something like this?