I just helped someone recently with this issue. The idea was to add a selected Model in Branch mode into the Associated model group list. I cheated when it was time to get the associated model group as you can see.
My vb script looked something like this:
'oModelLight is defined has a Model which contains all the scene ligths amongs other things...
set oLights = oModelLight.FindChildren("*",siLightPrimType, ,True)
for each light in oLights
'We just want to process the spot lights...
if light.ActivePrimitive.Parameters("Type").value = 2 then
set groupAL = Dictionary.GetObject(light&".light.Associated Models")
groupAL.AddMember oModel2Add ,True
End if
Next
-Martin