Display popup notification if date entered in column is less than 21 days

Question

I have a column named Date of Request and its type is Date and Time.

I would like to enable a warning popup message/notification when the user enters a date for a requested maintenance that is less than 21 days of today but still let the user enter the date (in case we can get approval in less than the 21 day window).

I tried using SharePoint's Column Validation using the below code, but this restricts the user to only enter dates outside the 21 day window.

=DateofRequest>=(TODAY()+21)

Is there an alternative option to accomplish this with JSON? I'm green and not super savvy with coding, just enough to kind of get by.

Any assistance would be greatly appreciated!

Answer 1

You can show some message on Header or Footer section using JSON formatting based on field values.

You can find sample Form Samples using JSON at below links:

https://pnp.github.io/List-Formatting/formsamples/

Below link help to with steps how to apply JSON in list forms.

https://docs.microsoft.com/en-us/sharepoint/dev/declarative-customization/list-form-configuration