Public Function Max_2(ByVal a As Long, ByVal b As Long) As Long
    If (a > b) Then
        Max_2 = a
    Else
        Max_2 = b
    End If
End Function
 
Public Function Max_3(ByVal a As Long, ByVal b As Long, ByVal c As Long) As Long
    Max_3 = Max_2(Max_2(a, b), c)
End Function
 
Public Function Max_4(ByVal a As Long, ByVal b As Long, ByVal c As Long, ByVal d As Long) As Long
    Max_4 = Max_2(Max_3(a, b, c), d)
End Function

Public Function Max_n(ParamArray n() As Variant) As Long
    Dim i   As Long
    Dim r   As Long
    Dim m   As Long
 
    r = (UBound(n) + 1) Mod 3
 
    For i = 0 To (UBound(n) - r) Step 3
        m = Max_4(m, n(i), n(i + 1), n(i + 2))
    Next i
 
    Select Case r
        Case 1
            m = Max_2(m, n(i))
        Case 2
            m = Max_3(m, n(i), n(i + 1))
    End Select
 
    Max_n = m
End Function

MsgBox Max_n(0, 1, 2, 3, 12, 15, 69, 0, 966)

Private Function max4(a As Long, b As Long, c As Long, d As Long) As Long
Dim m1 As Long: Dim m2 As Long
    If a > b Then m1 = a Else m1 = b
    If c > d Then m2 = c Else m2 = d
    If m1 > m2 Then max4 = m1 Else max4 = m2
End Function
 
Private Function MaxInArr(a() As Long) As Long
    For x = LBound(a) To UBound(a)
        If a(x) > MaxInArr Then MaxInArr = a(x)
    Next
End Function