Hi @solomojo
What I would suggest here is creating a published segment that is looking for contacts that have a 100 points or greater.
Then, you can create a Campaign that is going to look at the contacts in this segment and add an action step to this campaign that will update the contact fields or add a tag “Engaged 100+” which I think is a better option than having a custom field “Engaged 100+”
We would need more information as to how you intend on using this “Engaged 100+” in the future as there might be a few different options more efficient than creating a custom field “Engaged 100+”
Hope this helped.