If you could sort both sheets by the column  you're checking, your loop
wouldn't need to cover the whole range, would it? That would give you a
lot more speed. But I thnk once you have your value  from the first
worksheet (if it's sorted, then a simple Do...While should do the
trick), you shouldn't need to loop  through the second; a simple .Find
command should do it more easily and far, far more quickly.