MS Access forms 2007

Hello everyone,
I am using Access 2007 form with VBA as backend code. I have two combo boxes “beverages” and “range”. I have to display the value selected from the two combo boxes in a label box. I did that but a small modification is required. For Eg:Tea:10-20,Coffee:15-30,Juice:5-10 and if the customer again chooses “Tea:30-40” then the output result shud be like this Tea:30-40,Coffee:15-30,Juice:5-10. That is if the user selects a “beverage” which is already selected then it shud get automatically replaced.How to do this? We get display as Tea:10-20,Coffee:15-30,Juice:5-10,Tea:30-40 which is wrong.
Thank u.