Using "Data Validation" to Warn When a date is not within the current week

I'm trying to use Data Validation to have a warning pop up to the user that the date they entered is not within the current week and am not having any luck. I've been attempting to use the "Custom" option within the validation function but it's failing to work. I just want this to be a warning that alerts the user of the situation but doesn't prevent them from continuing with the date if it's correct. In the attached example, the last date entered (cell C9) should show a warning based on comparing that week number (cell D9) to the first week number entered (cell D5), but allow the user to either continue using that date or go back and correct it if it's simply a data entry error. Thanks in advance for any assistance!Sample Date Validation.xlsx

the custom Data Validation formula you need is: (this assumes your data starts in cell A2)
=WEEKNUM(A2)=WEEKNUM(TODAY())

Rich

---------- Post added at 09:49 AM ---------- Previous post was at 09:44 AM ----------

And to allow the user to continue, change the Data Validaiton Error Alert style to "Warning" or "Information" rather than "Stop".