wmi event watcher to look for mutiple files

I want to create a SQL Server SSIS package where I can watch a folder and once I have all (20 files) the required files I want to execute a sql statement. The files may come at different times and sometime they will be in csv and sometime they can come in zip. I know ssis has a wmi event watcher task but I’m not sure how I can specify to look for all 20 files. I guess I want wmi event watcher to look into that folder every 30 minutes and once it sees all the files move to the next step (execute sql task). Can someone tell me how I can specify all the file name in wmi event watcher task? If a file is missing then I want to look into the folder after 30 minutes. I want to move to next step after having all the files. Thanks.