Microsoft Access - Checking Duplicate Values in a field from a table

Good day everyone;

I would like to ask your inputs regarding duplicate values checking.

I have a form created the Saves all data entries. and under my save button
here are my codes.

DoCmd.DoMenuItem acFormBar, acRecordsMenu, acSaveRecord, , acMenuVer70
     MsgBox "Booking Transaction Saved.", vbInformation
     DoCmd.Close

I would like to add a condition where it could check if the given data from a textbox has a duplicate value in a specific field (Confirmation) in the tblBooking table.

Ex.
TABLE NAME: tblBooking

Fields
 DATE     BRANCH ID       BRANCH NAME     CONFIRMATION   PAYMENT   TAX    FINALIZER

Hope to hear from you.

Thank You sir James. for these references.


I will study on it....