Sub test()

Dim x As Integer

For x = 0 To 3
    MsgBox (ReturnRandomNumber(0, 3, x))
Next x

End Sub

Public Function ReturnRandomNumber(lower As Integer, upper As Integer, turn As Integer) As String
    
    Dim n As Integer, arr() As Variant
    
Redo:
    n = Int((upper - lower + 1) * Rnd + lower)
    
    ReDim Preserve arr(turn)
    
    ''' I want to store every n to check if the random number generated is repeated
    For Each a In arr
        If a = n Then GoTo Redo
    Next a
    
    ''' Within this function, the Array arr() does not store every n
    arr(turn) = n
    ReturnRandomNumber = n
    
End Function