Vista - Passing script function as a callback into .NET object

Mr Snover or anyone at the Powershel team,

I want to create an object which would listen for events and invoke a script
function that was passed in. For example:

function OnEvent($event)
{
#handle $event
}

#listen PSCmdlet would accept the handle to the OnEvent function somehow
listen -addr 127.0.0.1 -port 1234 -callback $OnEvent

keepalive #just sleep for some time letting the Runspace to stick around for
a while

Is there a way such scenario can be implemented? How can I pass a function
as a callback into the Cmdlet?

Thanks in advance,
Ilya