Pete, Interesting, for me, that you are asking about this. I think that I can help you with this if you would like to contact me via e-mail. I have just written a small, prototype program to "insert" a block into multiple drawings. With some, relatively minor, modifications this program could be made to search for any instances of a certain block, in each drawing, and then insert its replacement. Are you good with writing AutoLISP routines? If you wish, you can email me at WBFowler@bei-us.com and I will exhange ideas about this with you. Wayland