Workbook flash prevent

Muhammadiyya 

Make sure that your workbook contains a new worksheet called "Login" and change the Thisworkbook code to this:

Option Explicit
Public LoggedIn As Boolean

Private Sub Workbook_AfterSave(ByVal Success As Boolean)
    If LoggedIn Then
        HideOrSHow False
    End If
End Sub

Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
    HideOrSHow True
End Sub

Private Sub Workbook_Open()
    Application.ScreenUpdating = False
    Application.DisplayAlerts = False
    frmLogin.Show
End Sub

Sub HideOrSHow(justLogin As Boolean)
    Dim sh As Worksheet
    For Each sh In Worksheets
        If LCase(sh.Name) = "login" Then
            If justLogin Then
                sh.Visible = True
            End If
        Else
            If justLogin Then
                sh.Visible = xlSheetVeryHidden
            Else
                sh.Visible = xlSheetVisible
            End If
        End If
    Next
End Sub

In the code behind the userform, make these changes:

    ' Check if the entered credentials match
    If txtUserID.Text = userID And txtPassword.Text = password Then
        MsgBox "Login successful!", vbInformation
        Unload Me  ' Close the login form
'Next two lines are new
        ThisWorkbook.LoggedIn = True
        ThisWorkbook.HideOrSHow False
        ' Show the workbook and the HOME sheet
        With ThisWorkbook
            .Windows(1).Visible = True
            .Sheets("HOME").Visible = xlSheetVisible
            .Sheets("HOME").Activate
        End With

        Application.ScreenUpdating = True
        Application.DisplayAlerts = True
    Else
        MsgBox "Invalid User ID or Password", vbCritical
        txtUserID.SetFocus  ' Set focus back to User ID textbox
    End If

Finally, do not hide the application window (remove any Application.Visible = false)