Hotmail Style - "Select All" checkbox on a asp:checkbox - need little help

Hi,

I have OnClick script running off my asp:checkbox "Select All" that call a javascript function in order to check and uncheck all checkboxes... I got that part working fine,
Now, once I have selected all checkboxes and then uncheck one checkbox further down I want my "Select All" checkbox at the top to be unchecked...  That's part I cant seem to get working.

Here's my javascript so far and also my OnClick event from my asp:checkbox.  Hope to hear from you guys soon, thanks




function select_deselectAll (chkVal, idVal) {
                              var frm = document.forms[0];

                              // Loop through all elements
                              for (i=0; i<frm.length; i++) {

                                    // Look for our Header Template's Checkbox
                                    if (idVal.indexOf ('chxSelectAll') != -1) {

                                          // Check if main checkbox is checked, then select or deselect datagrid checkboxes
                                          if(chkVal == true) {
                                                frm.elements[i].checked = true;
                                          }
                                          else {
                                                frm.elements[i].checked = false;
                                          }
                                    }
                                    
                                    // Work here with the Item Template's multiple checkboxes
                                     else if (idVal.indexOf ('chxSelect') != -1) {
                                          // Check if any of the checkboxes are not checked, and then uncheck top select all checkbox
                                          if(frm.elements[i].checked == false) {
                                                //frm.elements[1].checked = false; //Uncheck main select all checkbox
                                                //frm.getElementById('chxSelectAll').checked = false;
                                                alert("uncheck master box");
                                                var myId = document.getElementById("chxSelectAll");
                                                alert(myId);
                                                //myId.checked = false;
                                          }
                                    }
                              }

                        }







<asp:TemplateColumn HeaderText="Workflow">
      <HeaderTemplate>
            <asp:CheckBox id="chxSelectAll" OnClick="javascript: return select_deselectAll(this.checked, this.id);" Text="All" Runat="server" Width="50px"></asp:CheckBox>
      </HeaderTemplate>
      <ItemTemplate>
            <asp:checkbox id="chxSelect" OnClick="javascript: return select_deselectAll(this.checked, this.id);" Runat="server" Width="50px" Visible=False></asp:checkbox>
      </ItemTemplate>
</asp:TemplateColumn>



The bug lies within the last part of my javascript function.