Google Search for Open Directories

Dan has been playing with Google, apparently:

Like most people that have heard of you, I have watched your vids etc and know that you could probably answer my question, so I will ll ask it. :) I have been designing a special google search which allows me to find movies in open directories. Here it is at its current state:

-inurl:(htm|html|php|shtml|3bb|aspx) intitle:"index.of"+(mov|mp4|m4v|avi)+"Name"+"Name2"+"Parent Directory"+"Size"+"last modified"+"description"-"jpg|mp3"

This covers and uncovers most things I need. There is one major hurdle before I can get much further. Most movies I am looking for are above 600MB. Here is a search which shows how it is possible to search by size:

-inurl:(htm|html|php|shtml|3bb|aspx) intitle:"index.of"+(mov|mp4|m4v|avi)+"Taxi"+"4"+"Parent Directory"+"700M"+"last modified"+"description"-"jpg|mp3"

As you can see, I changed the size to refine this search. When I search other things I do not know what size to search so I get many results. How do I do a search that basically says: ‘Above 600M’ to find me directories with results above 600MB, as many which do not have anything above that are useless?