Disable menuitem in a div on clicking button inside grid?

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C#

Javascript

There are three divs.
I have created a menu (navMenu) with 5 menuitems say a,b,c,d,e inside first div.
There is a grid(RGridMappedDocument) in second div which contains certain buttons.
There are two dropdowns in third div.
On clicking button inside grid, menu items b,c,d needs and the drop downs need to be disabled.
Using the below code am able to disable only dropdown.I ajaxified the dropdowns.
But when i did ajaxification the whole menu gets disabled on click
Please find a solution to disable only three menuitems on button click.

What I have tried:

onbutton_click(object sender,EventArgs e)
{
navMenu.FindItem("QA").Enabled = false;
navMenu.FindItem("Approve Synonym").Enabled = false;
navMenu.FindItem("Upload").Enabled = false;
ddSelectPriority.Enabled = false;
ddSelectResource.Enabled = false;
}

<telerik:AjaxSetting AjaxControlID="RGridMappedDocument">
                <UpdatedControls>
                    <telerik:AjaxUpdatedControl ControlID="RGridMappedDocument" LoadingPanelID="lPanelNoIcon" />
                    <telerik:AjaxUpdatedControl ControlID="RadTabStripClasses" LoadingPanelID="lPanelNoIcon" />
                    <telerik:AjaxUpdatedControl ControlID="ddSelectPriority" LoadingPanelID="lPanelNoIcon" />
                    <telerik:AjaxUpdatedControl ControlID="ddSelectResource" LoadingPanelID="lPanelNoIcon"/>                                                                                              
            </telerik:AjaxSetting>