How does Excel calculate the error in slope if the intercept is zero?

Hi all,

Given a set of discrete x-data and y-data points, how does the LINEST function calculate the slope error if the y-intercept is set to zero?

The post you gave does not exactly answer my question, although it is interesting to see how Excel calculates R^2 for constrained and unconstrained linear regression.

The LINEST function gives a standard error for the slope when the intercept is forced to go through the origin. In this case, I have no idea how Excel is calculating this error at all. I have tried several different methods but can't seem to get the same answer as the LINEST function.