change the script for the key so you have to be nearer it to pick up the key, or use a bigger box
edit: this should work-
;Artificial Intelligence Script
;Header
desc = Pickup Key
;Triggers
:state=0:hudreset,hudx=50,hudy=90,hudimagefine=gamecore\text\pickedupakey.tga,hudname=keyprompt,hudhide=1,hudmake=display,state=10
:state=10,plrdistwithin=10:state=1,playertake,coloff,plrsound=audiobank\misc\ping.wav,hudshow=keyprompt,hudfadeout=keyprompt
:state=1:rundecal=5
;End of Script
i changed the 'plrdistwithin' to 10 rather than 40
if you need it smaller then just edit it