How about this..
Assign ext 701 as a secondry extension to an existing user, this will then put two accounts on their device.
On the device program a key as being a line key for the secondry extension, now when they want to forward the calls they press that line key and dial *72external number
So on mine I have Yealink phones, so I set dss key 2 as a line key, label as Night/lunch whatever, and the line as Line2, they then press that button and do the normal forwarding.
My full setup is, during day time all calls are sent to extension 701, 701 is set to simultanisly ring for 0 rings and on no answer send calls to the desired Dial Plan or if fails also send to the Dial Plan - this means that all calls are sent to the dial plan as no one answers 701 within 0 rings.
I have then programmed a button on receptions extension called Night, this button is programmed as above, it's a line key that is set to use the 2nd account on the device ( ext 701) when they press this they dial *72externalnumber and thats it.
Now when any calls come through at night they come to extension 701 and rather than just getting no answer after 0 rings and being sent to the dial plan, they instead follow the forwarding.
I did program 2 buttons on reception, one dials *72number using line2 and the other button dials *73 using line2 to cancel it.