You can combine the bash script and applescript. Since Mac OSX is based on FreeBSD, you can create a bash script to delete the file. Then you can make an applescript to call the script and then start Word. Though thinking about it, you could do it all with applescript, just replace the first line with the applescript for deleting the file, which I can not think of off the top of my head:
do shell script “/path_to_script/rm_reg_cache.sh”
tell application “Finder”
open application file “Microsoft Word” of folder “Microsoft Office 2004” of folder “Applications” of startup disk
end tell