Option Explicit
Dim b As Byte

Private Sub test()
   Dim z As Long
   Use 5
   Use 6
   Use 6
   For z = 0 To 7
       Debug.Print z, Used(z)
   Next z
End Sub

Public Sub Use(ByVal n As Long)
   b = b Or 2 ^ n
End Sub
   
Public Function Used(ByVal n As Long) As Boolean
   Used = b And 2 ^ n
End Function

The function Used() tells us which numbers have been used.
How would you keep track of the number of times they have been used (in the
sample 5->1, 6->2)?