Ahhhh...ok. After reading the help file again, I see what I was missing. The BlockName is just to issue a new name for the model space being inserted. I was thinking it was pulling the block for the BlockName from the DwgFilePath.
I got something that works for me for now. I put a request in the Wish List for what you mentioned:
a return value from the lisp event handler that signals whether or not to run the default handler
What I was trying to accomplish was to have a textbox control on my form that would specify a uniform block scale and use that value to scale the block after it was dragged into the drawing using:
(setq obj (vlax-ename->vla-object (entlast)))
(vlax-invoke-method obj 'ScaleEntity scale rot)
For now, I've set up a button to scale the block after dragging it into the drawing using the method above. If anyone has a better suggestion, I'm all ears. As long as it doesn't involve WBlocking out all my blocks into a folder or set of folders. I like the way the blocklist control allows you to keep your blocks in one DWG file or grouped into a set of files (People_2D.dwg, Cars_Plan.dwg, etc.). Then all you have to do is add one folder to your support file search path and make a Combo Box as a filter for the DWG files in that folder. Anyway, just my preference.
-Kevin