Ok, I'll give you something to work on:
Append the code below to the acad2000doc.lsp file that we saved previously. Save the acad2000doc.lsp file, and open a drawing with a relevant title block in it (Replace the "YOURBLOCK" with the name of your titleblock).
(setq is_tb (ssget "x" '((2 . "YOURBLOCK"))))
(if is_tb
(progn
(setq qty_tb (sslength is_tb))
(if (= 1 qty_tb)
(alert "Yeah, I rock!")
(alert "Multiple Instances!")
)
)
(alert "Block Not Found!")
)
This will get you started. These are just basic boolean if's, that check for your title block. If more than 1 instance of the titleblock is found, you are prompted. If no title block is found, you are prompted as well.
I should be back tomorrow.