No it doesn't look possible through the GUI.
I found anumber of things I could not do with the Fritz!Box which had all worked perfectly with my previous Draytek router.
So I teated myself to a new Draytek 2860 and everything works perfectly again now.
The 2860 also does my AAISP ADSL line as well (with the addition of a Draytek Vigor 130 modem)
Line One:- Zen Fibre 1 - DrayTek Vigor 2860ac
Line Two:- Andrews and Arnold - DrayTek Vigor 130 Modem