Newbie: 2-dimensional array question

Hey All,
I’m brand spankin’ new to Flash, but need to developp a simple app for work.

I can get a 2-D array to work by setting it up like so:

i)
myDouble = [[1, 2, 3, 4],
[1, 2, 3, 4],
[1, 2, 3, 4],
[1, 2, 3, 4]];

But what if the array will actually be pretty big (say, myDouble[750][550]) and I want to loop through it to fill it up… I tried something like this, but it doesn’t quite work like I would expect it to:

ii)
for (var i = 0; i<100; i++) {
for (var j = 0; j<100; j++) {
//set all values to
myMap1*[j] = 0;
}
}

The weird thing is, if I do this:
myDouble = [[1, 2, 3, 4],
[1, 2, 3, 4],
[1, 2, 3, 4],
[1, 2, 3, 4]];

for (var i = 0; i<4; i++) {
for (var j = 0; j<4; j++) {
//set all values to 0
myMap1*[j] = 0;
}
}

Then, all values ARE in fact set to zero. So, I must not be declaring the array correctly in ii). Any tips?

Thanks!!