Checkbox Grid?

I'm trying to work out the best way of creating a multidimensional checkbox grid.
I have two sets of data one for the x axis and one for the y axis. How can I add the right amount of checkboxes and get data to and from them?
e.g.
        1        2        3        4
a      x        x        x        x
b      x        x        x        x
c      x        x        x        x
d      x        x        x        x
x's indicate places for checkboxes..............
I've been trying to do this for ages and just cannot work this one o ...