I am creating an Excel workbook which is multi-sheet & with many formulae
linking workbooks, sheets within the workbook & also operating within each
sheet.  Suddenly, the mouse pointer has gone "slow" and the actions of the
mouse on the first sheet are almost non-responsive - often requiring
multi-clicks (excess of 4) to get a response.    The same non-responsiveness
applies to selecting tool bar Options.     Why is this happening?  How do I
prevent it & how do I get rid of this situation on existing wokrbooks.    Not
all my Wookbooks display this problem.