Grouping objects

I have a slide which has a number of images and text that I grouped together.  I called this group "grp_01" .  I created an advanced action to hide grp_01 when a button is pushed.  Now I added more text objects to the slide.  I would like to add this new text objects to the "grp_o1", but I'm not sure if there is an easy method to accomplish this.  Right now, I ungroup the "grp_01" and select the items to be group, and then Group  Cnt+G.  But the reference to Grp_01 in the advanced action is gone.  Is there method of adding an item to a group without having to perform an ungroup?

Thanks.