Function Integral(x As Range, y As Range) As Single
Dim i As Integer, n As Integer
n = x.Rows.Count
If n < 3 Then Exit Function
Integral = (y(1, 1) + y(n, 1)) / 2
For i = 2 To n - 1
    Integral = Integral + y(i, 1)
Next i
Integral = Integral * (x(n, 1) - x(1, 1)) / (n - 1)
End Function




Function Simpson(x As Range, y As Range) As Single
Dim i As Integer, n As Integer
n = x.Rows.Count
If n Mod 2 < 0 Then Exit Function
Simpson = y(1, 1) + y(n, 1)
For i = 1 To n - 1 Step 2
    Simpson = Simpson + 4 * y(i, 1)
Next i
For i = 2 To n - 2 Step 2
    Simpson = Simpson + 2 * y(i, 1)
Next i
Simpson = Simpson * (x(n, 1) - x(1, 1)) / 3 / (n - 1)
End Function