First make sure you have all the blocks in separate DWG files. You'll also need to make a slide of each DWG drawing. Simply open the file normally, and at the command line type "MSLIDE". Name the file the same as the DWG so you know what you have.
Next create a mnu file to reference a layout your new menu. Make sure you keep a list of your block names so you know what to type in your mnu file. To use your new mnu file, type MENULOAD at the command line and browse to your mnu file. Be sure to reference the blocks directory into the support path of AutoCad. You will have to close AutoCad and re-open once you have added a new support path to your new blocks that your slide viewer menu references.
To see this mnu file example in action, download the entire blocks library at:
Scroll down to find: AutoCad 2000 JIC Electrical Symbols Menu Add-On 1.0
Follow the SETUP.DOC to install the new menu slide viewer into your toolbar. This does not alter your existing toolbars, it just adds to it. You can unload this menu set anytime by using MENULOAD command within AutoCad.