Help,Thank you very much

[oknixus]

First, when I enter 2 chars, the first line will be selected status,I could knock Enter key for input; But when I enter the third char, the selected status was missing, and I have to knock Ctrl-N to select the right one;
My problem is How to make the right one was selected when I enter the third char,the fourth char...the nth char.
My englist is not good; Sorry!
I need your help! Thank your very much!