Drop-down list searchable

I have drop-down list of more than 700 entries. Need make this drop-down list searchable by any character. For example, I have abece, abe, abec, aab, aebcee....that meen if i write ab, then shows abece, abe, abec. By default, Livecycle now offers the first character search, but need more for drop-down list. Any suggestion how do it?!