How do you grab the high lighted value from auto_complete_field after "Enter" event

Any Help is appreciated.....

thanks Perry.. I'll give it a shot..

So more Q... How do I grab that value and set it into params?
it seems like auto_complete_textfield does not put that value into
params automatically....

Any help is appreciated..

Perry.. Thanks.. But i'm using auto_complete_field and not
text_field_with_auto_complete...
I think from the example.. text_field_with_auto_complete does it
automatically..
but how do I feed the selected value into params when I'm using
auto_complete_field.

Any help is appreciated...