运行时总是出现错误9，“下标越界”？

Private Sub MSComm1_OnComm()
    Dim BytReceived() As Byte
    Dim strBuff As Variant
   
    Select Case Case 2
        MSComm1.InputLen = 0
        strBuff = MSComm1.Input
        BytReceived() = strBuff
        Dim i As Long
        For i = 0 To UBound(BytReceived)
           Debug.Print BytReceived(i)
        Next
        If i <= 2 Then
        Text2 = BytReceived(0)
        BytReceived(0) = 0
        Else
        tongyi = BytReceived(0)
        BytReceived(0) = 0
        fandui = BytReceived(2)
        BytReceived(2) = 0
        qiquan = BytReceived(4)
        BytReceived(4) = 0
        End If
    End Select