[jQuery] jQuery AutoComplete plugin & url problem

I am using a jQuery AutoComplete plugin.
My code is not working:

var jj=$("#region_area").val();
$("#code_area").autocomplete( "codearea.php?id="+jj , {autoFill:
true,matchContains: true});

This also not working:

var jj=$("#region_area").val();
jj="codearea.php?id="+jj;
$("#code_area").autocomplete( jj , {autoFill: true,matchContains:
true});

Help me pls.. and sorry for my bad english language.

Thank You