Treeview click event

Hi there   never use the treeview  and now i want to use for this project   but i dont know how to use 

the treeview commands 

i want to use like this   

Canada 

USA 

Portugal  

i want to click on  Canada and load the cities on a listview 

click on USA and  load the cities on listview   

click on portugal  and load a form1   like form1 show  

how i do this on treeview  

please help  

thanks