Your problem is twofold. First, as has been pointed out, your comparison should be
If (ComboBox1.SelectedItem = table1.Rows(index)(0)) Then
Second, you have no error checking, if you did, you would find out that iterating from 0 to Items.Count goes from 0 to 3. There is no index of 3 in your data table, so the code bombs out and it never hits the rest of your code. Change that to the following...
For index = 0 To ComboBox1.Items.Count - 1
Always remember that VB.NET uses 0-based indexing, so you only ever iterate to MaxArraySize - 1.