串口号不能改变,该如何解决

Private Sub Command2_Click()
Text3.Text = ""
Text1.SetFocus
If Combo1.ListIndex = 0 Then
MsgBox "请选择端口", vbInformation, "提示"
ElseIf Combo1.ListIndex > 0 And Len(Text1.Text) <> 15 Then
Text3.Text = "IMEI位数不对"
Text3.BackColor = &HFF&
Else
Text3.BackColor = &H8000000F
Dim portset As String  
portset = Combo2.Text + ",n,8,1"
On Error GoTo ER:
Dim comm() As String
comm() = Split(Combo1.Text, "M")
MSComm.CommPort = comm(1)
MSComm.Settings = portset
MSComm.PortOpen = True
Text3.BackColor = &HFF00&
Text3.Text = Combo1.Text + "初始化成功，连接手机中...！"
[color=#FF0000]ER:  Select Case Err.Number[/color]      Case Is = 8002
        Text3.Text = Text3.Text + "初始化失败:串口无效"
        Text3.BackColor = &HFF&
      Case Is = 8015
        Text3.Text = Text3.Text + "初始化失败：波特率无效"
         Text3.BackColor = &HFF&
      Case Is = 380
        Text3.Text = Text3.Text + "初始化失败：波特率无效"
        Text3.BackColor = &HFF&
    End Select
    On Error Resume Next
       MSComm.Output = "AT+ESLP=0" + Chr(13)
       Sleep 100
       MSComm.Output = "AT+ESLP=0" + Chr(13)
       Sleep 100
       MSComm.OutBufferCount = 0
       MSComm.Output = "AT+ESLP=0" + Chr(13)
       Sleep 100
       MSComm.OutBufferCount = 0
       MSComm.Output = "AT+ESLP=0" + Chr(13)
       Sleep 100
       info = MSComm.Input
       compa = info Like "*OK*"
       If compa = True Then
          Text3.Text = Combo1.Text + "与手机连接成功"
          Text3.Refresh
          Call Write_IMEI