Macro to watch Downloads folder for new files

I am trying to create 2 macros to monitor and reveal the new files in my Downloads folder. Macros 1 and 2 should perform the following functions:

  1. To store the names of all the newly added files in ~/Downloads to a temporary file
  2. To reveal all the downloaded files at once.

I will like this 2nd macro to wait if a newly added file is increasing in size or changing in its checksum and while this is ongoing, to keep checking for any newly added files. So, if 10 different files are added within 20 seconds of each other or one of the added files is a growing file, I get only one notification of all the files and all the files get revealed in the finder at once.

Can you please help fine-tune this? Thanks in advance.