Giving options for user to select from, storing selection as string

[#1]

Hi, here's my current code that displays a popup window for user input. 

I want it so that for Level:, they can choose between two options (each option having a box next to it that the user can tick to select one). What would I have to add to my code to get that? Here's a picture of what I want the "level" user input to look like:

Where the user can select one or the other before clicking "Save." Then, store "THIS" or "THAT" as a string depending on their selection. Thanks!

Note: If a dropdown menu is easier, that would work too. 

[#2]

Here is a simple example to show you one way of handling this

Names Default To Here( 1 );

r1 = Radio Box( {"This"} );
r2 = Radio Box( {"That"} );
New Window( "Example",
	V List Box( H List Box( r1, r2 ) ),
	Button Box( "Save",
	show(r2<<get);
		If( r1 << get == 2,
			theSelection = "This",
			theSelection = "That"
		);
		show(theselection);
	)
);
r2 << Group( r1 );