Difference between "empty" and zero?

I have a loop which runs through a range and stops when it hits the bottom of the range:

Do until activecell.value = empty
activecell.offset(0,1).activate
loop

However, the range has some zeroes in it, and the macro stops when it hits a zero. I don't want this to happen, a zero is a valid entry in this range. I just want it to detect when the cell has nothing in it.

This issue comes up a lot in my work, so can anyone suggest how to deal with it? That is, how can I differentiate between an empty cell and a cell with a zero in it?

Great, thanks a ton!