Well, in the post by Iddee above, (http://forum.beemaster.com/index.php/topic,30343.msg241770.html#msg241770
) it's mentioned that 1/4 works, 3/8 better, and finding the better is harder. I figure if you split the difference you will avoid the mouse problem and avoid the bee problem. How much work can that be in comparison to ridding the hives of infestation?
edit: Oh I see. Yeah that would be a lot of work. 8-)
What I was describing was a technique I had imagined where I would take #4 (4 wires per inch) hardware cloth (wire screen or galvanized mesh), then expand the size of every other hole to make a screen with a hole measurement of 5/16th of an inch. Greenbtree is saying that that's too big, a mouse can fit through a hole 7mm in size, while the size hole I'm suggesting is 8, and #4 hardware cloth will have 6mm holes.
It would look something like this:
And before anybody asks. Yes, I do have the equipment to measure little holes like that. I make flutes.