Question:  I’d like to be able to listen to the IFB mix on a panel.  Is there a way to assign the outgoing IFB mix w/interrupt to a listen button?   Basically I want to simulate what the people in the field are hearing on a panel.  

Answer:  The easiest way to accomplish this is by assigning an IFB listen key in EHX 8.5.1 to the desired panels for the selected IFB destination.
Follow the steps below to assign key and set its properties:
Open the Panel Menu in EHX and select the panel receiving the IFB destination listen key

• Select the IFB destination key and assign it as a listen
  
• Right click on the listen key to see the options for the key
  
• Select "Destination Listen" from the drop down list
• Select "ON", note that the green listen key changes slighty, the "IFB" area of the key is now gray indicating the feature is selected
• Apply the change to the EHX frame, the IFB destination key is now ready for use. 
  

The IFB listen key with destination listen activated will now mimic what the IFB talent will hear, forced listen program and program interrupts from the panel.