VB 下标越界，求大家指点一下，帮助！程序如下

For tmpi = 0 To 5
            txtRecieve.Text = Trim(txtRecieve.Text) & " " & IIf(Len(Hex$(getBytes(tmpi))) > 1, Hex$(getBytes(tmpi)), "0" & Hex$(getBytes(tmpi)))
            
          Next tmpi
          Text1.Text = CInt((getBytes(0) * 256 + getBytes(1)) / 4096 * 3300)
          Text2.Text = CInt((getBytes(2) * 256 + getBytes(3)) / 4096 * 3300)
          Text3.Text = CInt((getBytes(4) * 256 + getBytes(5)) / 4096 * 3300)
      Case comEvSend   ' 传输缓冲区有 Sthreshold 个字符  '
      Case comEvEOF   ' 输入数据流中发现 EOF 字符
    End Select

End Sub

getbytes(tmpi)提示下标越界！！不知道问题出在哪里