Live Receptionist to IVR feature code

We have been using an IVR for the main incoming DID but now have hired a receptionist and would like her to be able to use a feature code when available (phone rings) and when not (IVR). I can see quite a few possibilities such as DND to toggle available/not available. However I though I would ask for opinions as there are things I’m sure I haven’t thought of.

Thanks for any suggestions.

FreePBX 2.7
Asterisk 1.4
CentOS 5.7

In the latest release this is called a call flow toggle.