Make a delegate somewhere easy to reach by everyone like GameMode in my Example. Add Parameters as you like.
In your NPC´s, Characters or whatever at any time dispatch that event like that:
And in your Widget Bind to the Event from GameMode (Dont forget to assign your Gamemode properly)
Note: You have to bind to a Event just once BeginPlay or EventConstruct is enough. Don´t do it on Tick =)