You can add objects to the active selection set by using any of the following methods:
Adds one or more objects to the specified selection set.
Selects objects and places them into the active selection set. You can select all objects, objects within and crossing a rectangular area, objects within and crossing a polygon area, all objects crossing a fence, the most recently created object, the objects in the most recent selection set, objects within a window, or objects within a window polygon.
Selects objects passing through a given point and places them into the active selection set.
Selects objects within a fence and adds them to the active selection set.
Prompts the user to pick objects from the screen and adds them into the active selection set.
This example prompts the user to select objects, then adds those objects to the selection set.
' Create a new selection set
Dim sset As AcadSelectionSet
Set sset = ThisDrawing.SelectionSets.Add("SS1")
' Prompt the user to select objects
' and add them to the selection set.
' To finish selecting, press ENTER.