TOPIC: Pay scalar to cb field

I have a multiple site about a community builder field with a "pre paid" method.
I ask to you if it's possible to add a event with the scalar method.
Ex. User: Steven -> Field pre-paid $50,00 in the cb profile.
Steven select the football event ($5 to reigster) and the system scalar the $5 to $50,00 automatic.
Thank's