I have a library of blocks in C:\\BlockLibrary. I can make a custom command with this text in it "^C^C_insert 0atestblock \\;;\\" add that to a custom Panel, and add the custom panel to a custom Tab. If 0atestblock is already part of my drawing the button works. If I purge it out of my drawing the button gives me this message instead: "Cannot find the specified drawing file. Verify that the file exists."

How do I make a custom command that will insert blocks that are not already in my drawing file?

Do I need to put "C:\\BlockLibrary" into one of the File Location settings, or do I need to put my block library somewhere else, or?