The variance between two vectors is something that seems to be a bit ambiguous in meaning. I can think f at east a couple of ways you MIGHT have intended your request.
Perhaps you are asking how to compute a covariance matrix. Such a matrix would be a symmetric 2x2 matrix, contaiining elements for the variance of each vector, as well as the covariance between the two vectors.
If that is what you want, then you should read the help for the function cov, which should be perfect.
But if you want something else, then you need to more carefully explain your need.