Is it possible to change the acceptance raduis for 'ai move to' whilst the ai is moving? (Weeping Angel)

I am trying to get an AI character to only move towards the player when you are not looking at it (weeping angel) but I have a problem; when it starts moving after you have turned away if you look back it will not stop. I tried using a high acceptance radius so that it would stop which worked but if I looked away whilst I was standing close it wouldn’t move until I was out of that acceptance radius. Help! I have tried using float variables that change to a high acceptance radius when you look at the AI and a low acceptance radius when you look away but it appears that the acceptance radius stays the same through-out. Is there any blueprints that can allow the acceptance radius to be toggled? Thanks.