VB6 + QTP question

Hi guys I have a problem here is the code. So say post_no_message is 8 it will get the string compare it and at the 8th or last values it will throw out incorrect parameter error why? I just don't know any advice would be appreciated.



No_Messages=0
Post_No_Messages = Window("ChannelEditor").WinListView("Messages").GetItemsCount
For i = No_Messages to Post_No_Messages
CurrentMessage = Window("ChannelEditor").WinListView("Messages").GetSubItem(i,"Message")
If Instr(1,CurrentMessage,"Subsystem Name is undefined") > 0 Then
UndefinedCount = UndefinedCount +1
End If
Next