Check all checkbox in datagrid

 Hi all,
    I use a check box  to check and uncheck all other checkbox in the datagrid using javascript.
In IE its works fine,but in Morzilla  its not working.Plz help me.
Javascript:
function SelectAllCheckboxes(spanChk)
    {
    var oItem = spanChk.children;
    var theBox=oItem.item(0)
    xState=theBox.checked;   

        elm=theBox.form.elements;
        for(i=0;i<elm.length;i++)
        if(elm[i].type=="checkbox" && elm[i].id!=theBox.id)
            {
            if(elm[i].checked!=xState)
            elm[i].click();
      ...