list box and text box --drop down and selection problem

Dear Friends

I have a very good excel of selecting a list of names which are already feeded in the column AM.
When i enter a first few letters in column D where i want to enter a name ,a drop down will come like GOOGLE SEARCH and we can pick up a name by just clicking on it
but the PROBLEM is if there is no name in the list which we are looking for i have to type the full name and DOUBL CLICK it so that it will sit in the cell.

Here what i want is if i type a name which is not there in the list ,instead of double clicking that name,jsimply clicking enter or tab after punching the name that particular cell should catch the name ...because double clik make it time consuming when we enter 300+ records

I have attached the list

I greatly hope some excell genius over here can surely do this and help me
Kindly help me to solve my problem sir

Narayanan