I'm confused as to what you are asking in general, not specifically. What are you attempting to do with block.dwg file in your processes?
Importing the block.dwg file into an existing drawing should not cause that dialog to display and allow full function of the block. You can then export the block out into a block.dwg file. However, opening the block.dwg file should cause that dialog to appear as AutoCAD is alerting you to the fact it isn't really a drawing file.
To answer your specific question, there are 3rd party applications which can automatically select an option for a dialog prompt. Something similar to ClickYes.