How to get a listbox in listbox in Java when using zk?

Question

Please see my code below. I want to set lbProduct independently when they are not same.

I know that this code

page.setAttribute("snProductList", rmProductList);

can set it, but only when they all same.

How can I set them independently in Java code when they are not same?

<listbox id="lbSnList" rows="10" fixedLayout="false" width="100%"  model="@{uploadSnVo}" >
    <listitem self="@{each=SN}"  style="@{SN.BACKGROUND}">
        <listcell label="@{SN.SERIAL_NO}" />
        <listcell>
            <listbox id = "lbProduct"  hflex="1" mold="select"  selectedItem="@{SN.PRODUCT}">
                <listitem  forEach="${snProductList}" label="${each.name}"  value="${each.value}" />
            </listbox> 
        </listcell>
        <listcell>
           <checkbox id="cbCid" checked="@{SN.CH_GFLAG}" disabled="true" />
        </listcell>
    </listitem>
</listbox>