Autocomplete multiple values remote, strictly select/enter from suggested value

Autocomplete multiple values remote, strictly select/enter from suggested value

Hi,
I am using Autocomplete, with multiple values, remote.
It's working fine for me, but now I want to add one change in it.
The change is: I want to add condition that, user must select/enter value from suggested values in autocomplete.

e.g. Suppose my autocomplete suggesting following values on typing letter A :
      A003
      A004
      A005
Now user must select value from these suggested things, and if he enters wrong input (like A321 in above case), then, I would like to prompt user for correct input.

Can any one suggest what I need to do for this?

Thank you,
Bhushan