Where in the Microsoft Lync API can I set an event handler for incoming IMs?

I'm setting a handler for the InstantMessageReceived event, but it only seems to fire on outgoing text messages, not incoming. Here is the code I'm running:

# Register the app with Growl
$icon = "https://docs.google.com/uc?export=download&id=0B1Weg9ZlwneOZmY2b1NSVXJ0Q2s"
$types = '"new-im","new-call","invitation","share"'
& 'C:\Program Files (x86)\Growl for Windows\growlnotify.exe' /a:Lync /ai:$icon /r:$types "Registration."

#We just need the Model API for this example
import-module "C:\Program Files (x86)\Microsoft Lync\SDK\Assemblies\Desktop\Microsoft.Lync.Model.Dll"

#Get a reference to the Client object
$client = [Microsoft.Lync.Model.LyncClient]::GetClient()

#Set the client to reference to the local client
$self = $client.Self

# What do we do here?
$conversationMgr = $client.ConversationManager

# Register events for existing conversations.

$i = 0

for ($i=0; $i -lt $conversationMgr.Conversations.Count; $i++) {

Register-ObjectEvent -InputObject $conversationMgr.Conversations[$i].Modalities[1] -EventName "InstantMessageReceived" `
                    -SourceIdentifier "new im $i" `
                    -action {
                               $message = $EventArgs.Text
                               Write-Host "DEBUG: New incoming IM - $message"

                               # Try to get the name of the person...
                               $contactInfo = $Event.Sender.Conversation.Participants[1].Contact.GetContactInformation([Microsoft.Lync.Model.ContactInformationType[]] @("FirstName", "LastName", "DisplayName", "PrimaryEmailAddress", "Photo", "IconUrl", "IconStream"))
                               $name = " "
                               if ($contactInfo.Get_Item("FirstName")) { $name = $contactInfo.Get_Item("FirstName") + " " + $contactInfo.Get_Item("LastName") + ":" }
                               elseif ($contactInfo.Get_Item("DisplayName")) { $name = $contactInfo.Get_Item("DisplayName") + ":"}
                               else { $name = $contactInfo.Get_Item("PrimaryEmailAddress") + ":" }

                               # We need to check if the Lync window (conversation?) has focus or not.
                               if (1) {
                                  # We need to send our growl notification.
                                  & 'C:\Program Files (x86)\Growl for Windows\growlnotify.exe' /a:Lync /n:new-im /t:"New Instant Message" "$name $message" 
                               }

                            }
}

# If this exits, no more events.
while (1) { }

Every time I type out an IM message to someone else, it does what I'm trying to do for incoming messages. But nothing ever fires for those, just outgoing. I've been through all the documentation, and there aren't any other candidate events, I'm sure it's this one. But the Modality object just stores some stuff about whether it's an IM or screensharing and the like, nothing useful.

http://msdn.microsoft.com/en-us/library/lync/microsoft.lync.model.conversation.instantmessagemodality_di_3_uc_ocs14mreflyncclnt_members(v=office.14).aspx

Where am I screwing up on this? I prefer answers in Powershell, but I don't think this is a problem specific to Powershell, so if you know how to do it in C# or Visual Basic or something like that, I'd appreciate that too.

I don't have Lync so I can test this myself, but take a look at this link where it shows how to use the API.

The problem is(from what I understand) that there is a modality per participant per media. So for a conversation with two members using only text, there will be 2 modalities, one for incoming messages(from the remote participant) and one for outgoing. This is specified here in

Occurs when an instant message is received, or sent if the InstantMessageModality belongs to the local participant.

Source: MSDN

When you register your object-event, you register it to "your modality", and not the remote modality. To fix it it seems to you need to take each conversation from the manager, look at each participant except the one representing you (check the IsSelf property). Then take the modality from the participants(except yourself) and register for the InstantMessageReceived event.

At least that's what I got out of it, but as said I have no experience with Lync so I could easily be wrong.

My guess at how it could be done(VERY untested):

# What do we do here?  You get the manager the keeps track of every conversation
$conversationMgr = $client.ConversationManager

# Register events for existing conversations.

#You may need to use '$conversation in $conversationMgr.GetEnumerator()'
foreach ($conversation in $conversationMgr) {

    #Get remote participants
    $conversation.Participants | where { !$_.IsSelf } | foreach {
        #Get IM modality
        $textmod = [InstantMessageModality]($_.Modalities[ModalityTypes.InstantMessage])

        Register-ObjectEvent -InputObject $textmod -EventName "InstantMessageReceived" `
                    -SourceIdentifier "new im $i" `
                    -action {
                            #...

        }
    }
}