You never add the data in your Array to the list box. The only time you ever write data to the list box is here:
' clear the ListBox
If count = 1 Then
' create a header for the ListBox
outputListBox.Items.Add("Name" & ControlChars.Tab & _
ControlChars.Tab & "Mon." & ControlChars.Tab & "Tues." & _
ControlChars.Tab & "Wed." & ControlChars.Tab & "Thur." & _
ControlChars.Tab & "Fri." & ControlChars.Tab & "Total")
Dim output As String
End Sub ' DisplaySales
And this statement:
Dim output as String is unnecssary. You don't do anything with it, its declared at the end of your method, and is out of scope for all the other methods in your class.
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