Handle textbox and listbox combination

Question

Dear all....,
    Here i have an textbox and listbox.in runtime some datastored in listbox which is invisible.when i entered text in text that time listbox apper wiht text contains with respest to text in textbox.Up to now i got correct.Now my prob is after enter text in textbox list box apper and selest items in listbox through up and down arrows,after enter then the selected text in listbox placed into that textbox.For this my test program u find in attachment.Please help me to solve my proble...
Thanks in advance.

Regards,
VishnuVardhan D.