I get a file of dates and pricing from a 3rd party supplier. I copy this data
to another workbook in order to have all data in the one place to drive an
Access database and am careful to ensure that none of the original formatting
from the supplier's file is altered in any way. For some reason however the
date columns are never recognised to be in date format. In order for my
Access queries to function properly I have to manually enter each cell with
the supposed "date" value in the Excel workbook and double-click with the
mouse in order for the cell to change from General to Date format. Using the
format, cells, option from the menu doesn't have any effect. Unfortunately
each time I get new data this is an additional 45000 cells that need
attending to - I don't have the time or inclination to enter each individual
cell in order to resolve the problem. . .

Is there
a) a reason why this is happening?
b) a swift way of forcing the date format on the values in these cells?
c) some kind of macro that will allow me to solve the problem?

I've tried writing a macro to convert the format but it doesn't recognise a
value that can be converted - the only way of formatting values appears to be
the double-clicking on each cell.

Any help with this would be gratefully received!

Many thanks in advance,