Trigg a DIC in AC450
There exist one already. It is called Hot Keys - a keypress in the workplace while having an object in focus, faceplate open or mouse pointer hovering over a display element in a process graphic.
The script exposes a Verb the hot key may call.
Verbs can also be called from process graphics via Verb Invokers in PG2.
For 800xA for Advant Master, the verbs are located on Verb Map aspects on type level in the Object Type Structure.
It is also possible to run scripts from Terminal Window (DOS) via Aspect Automation code. This is less documented in the current users guides but I have posted examples on AKS.
The 800xA objects must be in an appropriate mode to accept orders from the HMI, eg Input Blocked. It is indeed possible to create verbs to transition objects between modes or simply write to the blocked property via OPC DA. However, I would use PC-program code to make sure the proper mode is always set (if a permanent block is desired).