Unfortunately I can't use SelectionSet, the user want to pick every single object. The command Select of Autocad would work but I think I could not get the ObjectId while the object are being select/unselect.
Here is the inferface of my program (sorry if there are spelling errors, it was in french but I change in to english for you), perhaps it's gonna be clearer if I explain more in details what I'm doing. The user want to calculate the lenght of a pipe network. So each time he click on an object, it shows the total length. He can hit pause to break a line or anything he need to do then he can restart is selection and continue to select object.