i'd do it differently:

vb Code:
  1. Public Class Form1
  2.  
  3.     Dim numbers As List(Of Integer)
  4.  
  5.     Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
  6.         numbers = New List(Of Integer)(9)
  7.         For x As Integer = 1 To 10
  8.             Dim number As Integer
  9.             If Integer.TryParse(InputBox("Enter an Integer"), number) Then
  10.                 numbers.Add(number)
  11.             Else
  12.                 x -= 1
  13.             End If
  14.         Next
  15.         numbers.Sort()
  16.         IO.File.WriteAllLines("numbers.txt", Array.ConvertAll(numbers.ToArray, Function(i) i.ToString))
  17.         Process.Start("numbers.txt")
  18.         MsgBox(numbers.Skip(2).Average)
  19.     End Sub
  20.  
  21. End Class