Thanks Harlan, but the biggest problem is that I work at a firm where any
rollout of new software is done on a corporate-wide basis and takes several
years to occur. If I could take the upgrade path then I would, but this isn't
available to me for several years.

With regards to the given solution, some steps are unclear, for example, why
a column of 1s is added and why the columns are switched around, hence the
explanation is not sufficiently clear in order to generalise. I am trying to
generate an Excel-based solution for some econometrics tests (specifically,
the Augmented Dickey-Fuller test which is specifically designed to account
for correlations in the lagged variables, and hence is guaranteed to generate
problems with multi-collinearity) and I would rather not be forced down the
route of switching to using Matlab instead of Excel.