Private Sub HighlightForm_Activate()

    With HighlightForm
        .StartUpPosition = 0
        .Left = Application.Left + (0.5 * Application.Width) - (0.5 * .Width)
        .Top = Application.Top + (0.5 * Application.Height) - (0.5 * .Height)
        .Show
    End With

End Sub

Private Sub UserForm_Activate()
    'Position top/left of Excel App
    Me.Top = Application.Top
    Me.Left = Application.Left

    'Approx over top/left cell (depends on toolbars visible)
    Me.Top = Application.Top + (Application.UsableHeight / 2)
    Me.Left = Application.Left + (Application.UsableWidth / 2)
End Sub