unselect a item in a listview

Question

Hi all,

i have a simple task, but i have no clue at the moment how to solve it.
I have a normal Listview-Box with some items.... (im working with VS2005, C#)

by clicking the first time, the clicked item is selected and blue highlited. now i want to unselect this item again by clicking an other time on it.

how can i manage this? which event can a take to solve this? thanks for your help.
woodi