Select Option dump

Hi,

I was following the blog /people/rich.heilman2/blog/2005/12/20/using-select-options-in-a-web-dynproabap-application

It works find when the values are entered in the fields of select options. But when these fields are empty

I get dump in the select statement as "Field Symbols has not yet been assigned".

select * into corresponding fields of table isflight from sflight

where carrid in <fs_carrid>

and connid in <fs_connid>.

Is there any procedure to use the select statement other than passing it to field symbols.?

Thanks in advance,