I figured out a way to do this. It's very inelegant, but it definitely suffices:
for i=1:50 (just 50, say)
data(:,2*i-1:2*i) = importdata(x);
!this stores all the data in a matrix, 2 columns of data at a time
Again, nothing fancy, but it works.
If I want all the first columns on the left side of the 'data' matrix and all the second columns on the right (instead of alternating first, second, first, second..) I suppose I can write to the data matrix like this:
But I haven't tried that yet.
Thanks for the ideas, everyone!