Thank you and that is why I am looking for a "generalized" inverse
matrix (a.k.a. pseudoinverse matrix?). With a search on Google, I
think an example is the Moore-Penrose Matrix Inverse (http://
mathworld.wolfram.com/Moore-PenroseMatrixInverse.html) and some
reasons for such matrix is to find "optimum" in an over/under
identified(?) system (http://www.cs.ut.ee/~toomas_l/linalg/lin2/
node15.html).

On second thought, I know Excel is not a matrix programming
environment, but it seems I need an algorithm to do singular value
decomposition, and I'd appreciate if someone could tell me if that can
be implemented in Excel (but not VBA if possible). Thanks in advance.

Regards,
Y. F.