Extending a little on bens solution
Names Default To Here(1);
options = {"1", "2", "3", "4", "5", "6", "7", "8", "9", "0"};
initial_option = "7";
nw = New Window( "Test",
combob = Combo Box(options, << Set(Contains(options, initial_option)))
);
Scripting Index is usually good place to start

-Jarmo