do you get the point ?
Hi Adrian,
not really, but that doesn't matter. The point / problem with your database and code is that you have Text instead of real date/time in the cells.
I know you think it doesn't matter, because the formula in D,F,H,J works... but why is that is a different story.
Trust me that is an error and it must be corrected:
Columns E,G,I,K is Text and you have errors:

On a German system you can see that all dates with a dot as separator are valid, all others are text and wrong and invalid too:

If you have text in the cells, your file will never work. That is the point.
Change all date/times to real date/times in the sheet.
Use Date variables as Ossie suggested
Use code with CDate and FormatDateTime and write the Date variables into the sheet and your problem is gone.
Andreas.