record duplicated in combobox

Hi People,

I have two combobox that are genereted from selects, a father and a son.

My problem is that when i change the in  first combo, in the second combo apears the first record from the combo father, plus all the records of the combo selected.

follow the code:

<!---<SELECT NAME="IDreg">
                 <CFOUTPUT QUERY="Reg">
                 <OPTION VALUE="#IDreg#">

                <CFIF IDreg EQ IDreg><OPTION VALUE="#IDreg.IDreg#"<CFIF IDlinha EQ
IDlinha> SELECTED</CFIF>>#descricao</OPTION></CFIF></CFOUTPUT>

                </CFOUTPUT>
                         </SELECT>--->