CAD tip # 5351:

First save the edited block to a separate DWG file (using WBLOCK). In the target drawing first load (APPLOAD) the BlkRedef utility and use the BLKREDEF command to update (refresh) the blocks of a given name. The BlkRedef command with the parameter blockname can be used even in scripts to batch update multiple drawings at once (use any batch processor - like ScriptPro or ScrGen).

In your script, use e.g.:

(load "blkredef.lsp")
BlkRedef MYBLOCK1
BlkRedef MYBLOCK2
BlkRedef MYBLOCK3
save
quit