The script can go whereever you want, specifying the full path in the trigger. Adding the /main.txt should suppress the output.
e.g. ... SHELL 'c:\morph3\texis.exe -r db=$db table=$table tbname=project c:\morph3\texis\scripts\populatelog/main.txt'
e.g. ... SHELL 'c:\morph3\texis.exe -r db=$db table=$table tbname=project c:\morph3\texis\scripts\populatelog/main.txt'