Conditional formatting - If cell value is a date, copy to another cell and show text

Hello!

I would like to apply conditional formatting such that if the value of any cell in column C (see attached sample workbook) is a date, then it will automatically copy that date into column B but also display that date in column B as the text "Not applicable" (so that I can still use date filtering from either column.)

It's better explained in the sample workbook attached.

Thanks in advance!

Can anyone help with this? Thanks.

Also can use VBA if that would be a better way to do this.