Test.xlsm

In the above workbook I have a code that puts the info within a combo box in a another cell on the sheet. Is there a formula or vba to say for instance if J.Doe is in this range then do not put it in again? my combo box require EE to enter their password after choosing there name, If they enter a wrong password it leaves the combo box empty but still enters it in the other cell. I don't want it to do this. EE example wold be frank Workman password 18026