Табулирование функции

Private Sub Command1_Click()
Dim x0 As Single, xn As Single, a As Single, b As Single, h As Single, z As Single, X As Single, Y As Single
x0 = 1.5: xn = 4.5
a = 3.5: b = 3: h = 0.1
For X = x0 To xn Step h
    If X <= a Then
        z = Sin(X)
        Else
        If a < X And X < b Then
            z = Cos(X)
            Else
            If X >= b Then
                z = Tan(X)
                Else
                z = -1
            End If
        End If
    End If
    Print Format(X, "#.#"), ;
    If z <> -1 Then
        Y = (z ^ 2 + X) / Log(2 + X ^ 2)
        Print Y
        Else
        Print "Не определено"
    End If
Next X
End Sub

If X <= a Then 
   z = Sin(X) 
ElseIf a < X And X < b Then 
   z = Cos(X) 
ElseIf X >= b Then
   z = Tan(X) 
Else
   z = -1
End If

 
z = - 1
   Select Case True
        Case X <= a: z = Sin(X)
        Case a < X And X < b: z = Cos(X)
        Case X >= b: z = Tan(X)
    End Select