Private Sub CommandButton1_Click()
Dim a, b, h As Single
Dim x, y As Single
a = CSng(TextBox1.Text)
b = CSng(TextBox2.Text)
h = CSng(TextBox3.Text)
x = a
Do While x <= b
If x < -1 Then
y = x * x
ElseIf x >= 1 Then
y = 3 * x
Else
y = -x ^ 3
End If
ListBox1.AddItem (CStr(x))
ListBox2.AddItem (CStr(y))
x = x + h
Loop
End Sub