X,Y,Z Coordinate Generator with numbered labelling based on ranges

Hi everyone, I am trying to work out the best way to have a script created. at the moment we import CAD layouts of housing developments in to Max, and we place 3d models of houses over that layout.

What I would like to do is click the bottom left of each of the CAD house blocks and create a 'point node' in that node I would like it labelled in order of clicks. So if I click Plot 01, the helper is called 'P01', if I then click the corner of Plot 2 the helper is called "P02". if for what ever reason the start of the plots is not starting from 01 then I would like to be able to set the script to start from a certain number. i.e set first plot to "P500" and continue from there. Additionally if I wanted to reset back to a new number, it would reset any additional clicks to the start of the number.

my aim is then to import this in to Unreal Engine, as we have already got it set up to read from Salesforce and pull a X,Y,Z digital, however on the first upload we would populate salesforce. we can script this easily with visual prep manager in unreal, I just need the information from somewhere. Ideally I would get this straight from CAD however the team that plots CAD does not assign any plot specefic data to a block, so this sounds like the next best place to pull it.