First off why a listview? Why not a label or a textbox?
How many items are in the listview? The items are in a base 0 array so if it's just one item it's index will be 0.
Here is a simple example. (In this sample i use the Button1.Click event. you would obviously use an event that trigers when the calculations are made.)
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
ListView1.Items.Item(0).Text = "good bye"
Finally what does this have to do with Visual Basic .NET list view is a COM control.