请高手帮忙写个vb代码，实现当输入信号值时，点击计算得出电流值；当输入电流值时，点击计算得出信号值

Option Explicit

Dim signalIndex As Byte

Private Sub Form_Load()
  Combo1.Clear
  Combo1.AddItem "请输入信号类型", 0
  Combo1.AddItem "压力", 1
  Combo1.AddItem "差压", 2
  Combo1.AddItem "温度", 3
  Combo1.ListIndex = 0
End Sub

Private Sub Command1_Click()
  signalIndex = Combo1.ListIndex
  Select Case signalIndex
    Case 1, 2, 3
      If Text3.Text <> "" Then
         Text4.Text = Val(Text3.Text) * signalIndex * (Val(Text2.Text) + Val(Text1.Text))
      Else
         Text3.Text = Val(Text4.Text) / signalIndex / (Val(Text2.Text) + Val(Text1.Text))
      End If
    Case Else
      MsgBox "请选择信号类型"
  End Select
End Sub

Private Sub Command2_Click()
  Unload Me
End Sub