The instruction to call a block from a dwg are in Lee's Steal.lsp you should read 1st, I have used it and it works well, just trying to remember which bit of code its in.
; cut a bit out of the code
(if (not steal)(load "Stealv1-6"))
(Steal <Dwg> <ItemList>)
dwg obvious full pathed dwg name
(Steal "C:\\My Folder\\MyDrawing.dwg"
'( ("Blocks" "Block1" "Block22") )
)