Testing for statistical significance with 2 scores?

I am using a formula which calculates z scores based on random v expected conditions. The result is a z score for the group at Time 1 and then at Time 2 along with the standard deviation at each time point. I want to compare the two z scores for statistical significance but cannot use the t-test because I only have two values (I think). I thought calculating the confidence limits might help with this but now I don't even know if this is possible!! Any help is much appreciated on how to test for significance in this case.