Public Class Form1

    Dim i As Integer

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        i = i * (-1)

        If i = -1 Then

            Label1.Text = "Текст перший, коли i = 1"

        Else

            Label1.Text = "Текст другий, коли i не = 1"

        End If

    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        i = 1

    End Sub

End Class