How to pop up a warning but still allow saves when users input duplicate values?

If you wish to prevent users from creating duplicated entries, you can set up the "Unique" attribute.

Sometimes, we would like the system to pop up a warning but still allow saves when users input duplicate values. For example, we want to prevent users from creating duplicated entries for the same customer in the "Contacts" sheet. However, there are cases where clients might have the same names. Hence, we would like to be notified before we save the entry and check if the entry is duplicated.

You may follow the steps below:

Step 1. In the "Accounts" sheet, create a link and load field and link to the "Contact Name" field:

Step 2. On the field you created in step 1, apply formulas to reference the "Contact Name" field:

Step 3. Save the design and trigger the formulas recalculation.

Step 4. Set up conditional formatting based on the field so it will pop up warning when there are duplicated values:

In the future, when users input duplilcated values, the system will pop up the message:

You may click the "Ok" and then save the entry still.