How to update the default directory

My use case calls for the movement of a file name meeting a specific pattern to get moved from the ~/Downloads directory to a n application specific directory and then either open the file using excel or run a python script on that file. I can get it to work if I hard code the directory and new filename to to the excel / python calls. Is it possible though to extract the filename from the path store it in a new hazel property and also change the default directory so the excel call in a script command would be something like 'excel ${new file}' and have it run as it was in the new directory?

Thanks in advance for your assistance.

Maybe I'm not following but Hazel does pass in the path of the file being processed into any scripts. Not sure where hardcoding is needed. Could you elaborate?