You mean the data entry form is the "main" form? You can set menu item to disabled (Enabled = False).
Or you don't even have to do that. If the user selects "Open Summary" (and the file is empty) the user gets an empty summary form.
Here's a fixed "Read Data"-button, which checks first that the file exists. It also closes the StreamReader, a minor bug in my previous posting:
Private Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click
'
Dim i As Integer
AutoCount = -1
If Not My.Computer.FileSystem.FileExists(FileName) Then
Exit Sub
End If
Try
autoStreamReader = New StreamReader(FileName)
Do Until autoStreamReader.EndOfStream
AutoCount += 1
ReDim Preserve Autos(AutoCount)
Autos(AutoCount).Model = autoStreamReader.ReadLine
Autos(AutoCount).Manufacturer = autoStreamReader.ReadLine
Autos(AutoCount).Year = autoStreamReader.ReadLine
Autos(AutoCount).VIN = CInt(autoStreamReader.ReadLine)
Loop
Catch ex As Exception
' Handle exception
Finally
autoStreamReader.Close()
End Try
'
For i = 0 To AutoCount
ComboBox1.Items.Add(Autos(i).VIN)
Next i
'
End Sub