Yep VBA reactor .. I keep the built in reactor turned off by default.
Mine basically has events tied to specific types of entities and specifically named blocks.
For example, if I double click on text it opens the appropriate text editor whether it is mtext, attdef, dtext etc. Certain blocks when double clicking opens my personal enhanced attribute editor.
I have used other ideas in the past, for example, whenever I placed a cut section or detail mark, I could double click on it and open or change to the appropriate drawing and zoom in on the detail.