diff --git a/src/lib.rs b/src/lib.rs
index 89c5cbd..654ff28 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -491,3 +491,61 @@ impl MessageBehavior for VmcExtCon {
         });
     }
 }
+
+struct VmcExtKey {
+    active: bool,
+    name: String,
+    keycode: i32,
+}
+
+impl MessageBehavior for VmcExtKey {
+    fn to_sendable_osc_message(&self) -> OscMessage {
+        let mut args: Vec<OscType>;
+        if self.active {
+            args = vec![OscType::from(1)];
+        } else {
+            args = vec![OscType::from(0)];
+        }
+        args.append(&mut vec![
+            OscType::from(self.name.to_owned()),
+            OscType::from(self.keycode),
+        ]);
+        return OscMessage {
+            addr: String::from("/VMC/Ext/Key"),
+            args,
+        };
+    }
+    fn parse_from_osc_message(msg: OscMessage) -> Result<Self, String> {
+        if msg.args.len() != 3 {
+            return Err(String::from("arg count invalid"));
+        }
+        let active: bool;
+        let name: String;
+        let keycode: i32;
+        match msg.args[0] {
+            OscType::Int(i) => {
+                if i == 1 {
+                    active = true;
+                } else if i == 0 {
+                    active = false;
+                } else {
+                    return Err(String::from("arg value invalid"));
+                }
+            }
+            _ => return Err(String::from("arg type invalid")),
+        }
+        match &msg.args[1] {
+            OscType::String(s) => name = s.to_owned(),
+            _ => return Err(String::from("arg type invalid")),
+        }
+        match msg.args[2] {
+            OscType::Int(i) => keycode = i,
+            _ => return Err(String::from("arg type invalid")),
+        }
+        return Ok(VmcExtKey {
+            active,
+            name,
+            keycode,
+        });
+    }
+}