Create a block with contextual filter that show related nodes based on field value, not with taxonomy I'm no newbie to Views or Argument/Contextual Filters, but I'm having trouble getting my head around a (simple) view.

I've created a Content-type "Event". 
Which contains an 'Addressfield', which I use to store an Address and Geocode it to an value which I store in Geofield.

What I'm trying to accomplish is a 'related nodes' block, similar to an 'related articles' based on taxonomy. In that case you make a relationship, and use the NID in de URL.

I've created a View: 
- a block style.
- added a 'contextual filter #1':
- When Filter value is not available: 'provide default value', content id from URL.
- Extra: exclude. This filter excludes the current node.

I'm having trouble getting to the next step: I only want to show the nodes which have the same country as the current node. How do I accomplish that?

So if I'm visiting a node from 'France', I only want to show related nodes from France.
You can try using PHP code in the contextual filter. You will be able to load the Node using arg(1) - node ID and provide the field value based on the node. Refer screenshot.