David,

You could use the worksheet change event, but we would need a _little_ more info to help you figure
out what to do....

HTH,
Bernie
MS Excel MVP


"DavidM" wrote in message
...
At present when I change the start date in one cell and end date in another
cell the number of weeks difference between the dates is automatically worked
out by a formula in yet another cell.

I have recorded macros to alter data in different sheets of the workbook
according to the number of weeks difference. But I would like to do it
automatically on entering the dates.