Using encodeURI with text_field_with_auto_complete

I am using text_field_with_auto_complete to display a list to the user.

Unfortunately, some of the items contain non-url friendly characters.

How can I wire up the prototype encodeURI function to package the field
before sending?

<%= text_field_with_auto_complete :classification, :class_desc ,
:skip_style => true, :size => 60 %>

Thanks for any tips