Hi! can someone give me idea and how?

i want my combobox when i type letter all item has the letter i have typen will show in the combobox.... because in the current situation in vb .net when i type "A" all item that start from a will display i want this time when i a letter "A" all those have the letter "A" will display..

is it posible? how to do? please give me sample program and idea