overwriting 'venue' with another plugin

Hi Kev & Co.

I just wanted an insight into how I may be able to overwrite the 'venue' input when creating an event.

I have created a plugin that allows users to submit places, venues. So I'd like to overwrite the event calendar so one of the places that already exists in my plugin MUST be used when holding an event?

I have no problem creating an array full of myplugin->titles but not sure where to start in doing something to the event calendar from my plugin. Obviously I'd like to not have to fiddle with the event calendar as I expect/assume nice updates and improvements as time goes on.....

Thanks - any help greatly appreciated... :)