Continually check for file

I need a script or bat that will open a saved session and put a trigger file(trigger.txt) to the ftp server then continually or loop to check for a generated file(trigger.blt) for up to 5 minutes or I suppose until the file is present then pull or get a different file(downlaod.txt)
I've tried various ifnot errorlevel checks etc but can't seem to figure out.
Any help is much appreciated!