Type of game and mission

I would create a GUI for select a different type of game and consequently different type of mission...
Example....
I select ingui a Type of game "DeatMatch"
and see only mission in list of type "DeatMatch"
In game.cs have this ->

$Server::GameType = "FPS Starter Kit";
---
$Server::MissionType = "DeathMatch";

I cretate a button to change this variable? -> $Server::MissionType = "DeathMatch";