Private Function Fibbo7913(Optional Limit As Long = 4000000) As Long
Dim aux  As Long
Dim act  As Long
Dim ant  As Long
Dim suma As Long
    ant = 1
    act = 1
    suma = 1
    Do
        If act And 1 Then suma = suma + act 'operacion binaria que me dice si es par o no
        aux = act
        act = act + ant
        ant = aux
    Loop While act < Limit
    Fibbo7913 = suma
End Function
 

Private Sub Form_Load()
    Debug.Print Fibbo7913
End Sub

524288 '// debería de ser: 4613732

Private Function fb(Optional lLimit As Long = 4000000) As Long
Dim fn As Long, f1 As Long, f2 As Long
If lLimit And &H80000000 Then Exit Function
f1 = 1
f2 = f1
Do While f2 < lLimit
fn = f1 + f2
f1 = f2
f2 = fn
 If fn Mod 2 = 0 Then
fb = fb + fn
End If
Loop
End Function