请教各位大神,在VB中如何计算余误差函数(erfc)

Public Function 复化辛普生积分(a As Double, b As Double, n As Integer) As Double         'a、b为积分上下限， n为积分区间划分份数
Dim dx As Double, i As Integer, m As Integer
m = 2 * n
dx = (b - a) / m
复化辛普生积分 = f(a) + f(b)
For i = 2 To m Step 2
    复化辛普生积分 = 复化辛普生积分 + 4 * f((a + dx * (i - 1))) + 2 * f((a + dx * i))
Next i
复化辛普生积分 = (复化辛普生积分 - 2 * f((a + dx * m))) * dx / 3
End Function


Function Integration( a As Double, b As Double)  '矩形方法，a、b为积分上下限，次数由精度控制
Dim h As Double, x As Double
n = 2
s = 0

p = f(a) + f(b)
Do

 h = (b - a) / n / 2

 s2 = 0

 x = a + h

 s4 = f(x)

 For i = 2 To 2 * n - 1 Step 2
  x = x + h
  s2 = s2 + f(x)
  x = x + h
  s4 = s4 + f(x)

 Next i

 

 s = h / 3 * (p + 2 * s2 + 4 * s4)

 If (Abs(s - s0)) / Abs(s) <= 0.000001 Then Exit Do  '误差精度
s0 = s

 n = 2 * n
Loop

Integration = s

End Function


Function f(x as double) as double

 f= 1/x                    ' 积分符号内部的表达式， 这里是f(x)=1/x
End Function