Private Sub OK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOK.Click
        If Not (txtUsername.Text = "" Or txtPassword.Text = "") Then 'check if txtbox is empty
            If varCounter = 4 Then 'check if number of tries is 4
                MsgBox("You have reached the allowed number of tries. The program is now shutting down.", MsgBoxStyle.Exclamation)
                Me.Close()
            Else
                connLogin.Open() 'Open database
                'read from database
                Dim connLIcmd As New SqlCommand("SELECT Logn_Username, Logn_Password FROM User_Login WHERE Logn_Username = '" & txtUsername.Text & "' AND Logn_Password='" & txtPassword.Text & "'", connLogin.Conn)
                Dim r As SqlDataReader = connLIcmd.ExecuteReader()

                If r.HasRows = 0 Then
                    MsgBox("Either username or password is incorrect. Please try again.", MsgBoxStyle.Exclamation) 'display error msg
                    r.Close() 'close reader
                    varCounter += 1 'add 1 to counter
                    connLogin.Close() 'close database

                    txtUsername.Text = "" 'reset login form
                    txtPassword.Text = ""
                    txtUsername.Focus()
                Else
                    varCounter = 0 'reset counter
                    r.Close() 'close reader
                    connLogin.Close() 'close database

                    txtUsername.Text = "" 'reset login form
                    txtPassword.Text = ""
                    txtUsername.Focus()

                    'hide login form and show main form
                    Dim frmCopy As New frmMain
                    frmCopy.Owner = Me
                    frmCopy.Show()
                    Me.Hide()
                End If
            End If
        Else
            MsgBox("Please fill in the required fields.", MsgBoxStyle.Exclamation) 'display error msg
            varCounter += 1
        End If
    End Sub