Superset Speakerphone in-use indicator

[thesavo]

We are using SX2000 Switch cabinets and a 3300 ICP.

I have searched and found that this question was asked in the following threads.
http://mitelforums.com/forum/index.php/topic,4832.msg20977.html#msg20977
http://mitelforums.com/forum/index.php/topic,2854.msg11261.html#msg11261.

My question is a little different.  I  primarily answer helpdesk calls using the speaker phone on my SuperSet 4150 or my Lab phone Superset 4025.   I don't use a headset.  Is there a way for DNI phones to trigger an in-use indicator without using the hand set?
Something like these exist but they seem to be useful for POTS lines.   Is there away for the the large Message Waiting indicator on the top of the superset to function likea DSS/Busy Lamp while I am on the speakerphone?  I am not able to close the door to my office otherwise I would.   Passer-by's take the hint when the handset is up-to my head.  But when I am on speakerphone call they walk-in an start talking.   I have brought this up to my manager and he mentioned that he also would like the same thing but he hasn't found the answer either.  Being in IT I need my handsfree to type and take notes. 

I thought of using a 2nd pair and hooking up a second superset.  Then filling the softkeys with DSS/Busy lamps for the helpline KEY SYSTEM extension.   I don't want to have to hookup N+1 phones for every one in IT. 

[johnkeri]

Might sound silly!
Get a small night lamp and turn it on manually.

[thesavo]

I have thought of setting up an "on-air" sign.  I am sure there are too many TDM or DNI protocols to make a universal device.   I was hoping someone else had this issue and found an in-band or automatic solution.