MFX OnInput method question

 Dear All, I’m implementing an MFX plug-in that uses InputPulse, so I can have my OnInput method called periodically. I accumulate the value of GetPulseInterval on every call, except the calls when there is data to process in the input buffer, to measure time passed. But, there is a problem I don’t know how to solve yet. It goes like this: My OnInput method is being called even if a voice message comes in via a Midi InputPort that is not being assigned to the actual track, and I don’t know how to differentiate between these extra OnInput calls and the needed calls triggered by InputPulse? Input buffer is empty in both cases, which makes it impossible to separate. Could you please help me with this? Is there a way to somehow let my app know if the OnInput method was triggered by a Midi port not used on the given track? Thank you in advance!