I have this download manager and I want to know which of the many executables to place in the “Perform virus check” field, and also which “Arguments” can I use.
Paultx
Welcome to the forum.
If you installed Avast in the default Folder then, this is all you need:
C:\Program Files\Alwil Software\Avast4\ashQuick.exe
Arguments are usually not needed.
If, for any reason, you need any argument (which is not common), try:
%f
or
%d 
Thank you, bob3160 and Technical.