Selecting an Item in Combo Box when specific key is pressed

Hello,

Guys I want to implement some functionality in Combo box. Hope you guys can help me out.
I want to implement functionality such that when user presses any character then first entry of that character is highlighted.

For example. In drop down I have following value.

Apple
Ball
Cat
Carrom
Dog
Doll
Zebra

Now if user clicks on Combo box Arrow and presses C then “Cat” is highlighted in drop down. If it again presses C then “Carrom is highlighted” and so on. If it presses Z then “Zebra” is highlighted.

Hope the description is meaningful.

Thanks in advance.