Option Explicit
 
Const n = 12
 
Private m_xQuer As Double
Private m_Sigma As Double
 
Public Property Let xQuer(dummy As Double)
     m_xQuer = dummy
End Property
Public Property Let Sigma(dummy As Double)
    m_Sigma = dummy
End Property
Public Property Get xQuer() As Double
    xQuer = m_xQuer
End Property
Public Property Get Sigma() As Double
    Sigma = m_Sigma
End Property
Private Function f() As Double
Dim i As Integer
Dim dummy As Double
 
For i = 1 To n
    dummy = dummy + Rnd()
Next i
 
f = dummy - n / 2
 
End Function
 
Public Function NormRnd() As Double
 
NormRnd = xQuer + f * Sigma
 
End Function