The following code will iterate over every object on a sheet and tell you which objects are active BUT the problem is when you click a button to trigger the macro, the button becomes the sole active object!!
for i=lbound(objs) to ubound(objs)
if objs(i).IsActive then msgbox objs(i).getObjectId & " is active"
... not sure if assigning the macros to the menu bar (Macro 1, Macro 2, Macro 3) would fix this, but you also have the issue if multiple objects are selected.
Perhaps you could place all your charts into a container and use the following to identify the chosen chart ...
set ContainerObj = ActiveDocument.GetSheetObject("CT01")
The example in APIGuide shows it should be possible to identify the ActiveObject Id (ContProp.ContainedObjects.Item(0).Id) but this doesn't work in QV11 it seems, you might need to put the actual object ID via the container properties object labels (Objects Displayed in Container).