Autocomplete dropdown with stop propagation?

I have recently found that my autocomplete extender drop down menus on my asp.net website do not function correctly on tablets. Basically when a user clicks on the scroll bar the drop down menu closes and the user cannot make a selection. After much reading I think I somehow need to add a "event.stopPropagation();" function to my page. I am not familiar with this at all. So I have an "AutocompleteExtender" "AutoCompleteDropDownPanel" and a textbox for text input. Any ideas how I can apply the event.stopPropagation();" to my page or to the extender? TIA

<asp:AutoCompleteExtender ID="AutoCompleteExtender" runat="server"
DelimiterCharacters="" Enabled="True" ServicePath="AutoComplete.asmx"
        ServiceMethod="GetCompletionList" TargetControlID="DoctorNameTextBox"
        UseContextKey="true" ContextKey="StateDropDown"
        onclientitemselected="getSelected"
        ShowOnlyCurrentWordInCompletionListItem="True" CompletionInterval="100"
        MinimumPrefixLength="2" CompletionListElementID="autocompleteDropDownPanel"
           CompletionListCssClass="style101"></asp:AutoCompleteExtender><asp:Panel ID="autocompleteDropDownPanel" runat="server" Font-Size="Medium"
    HorizontalAlign="Left" Wrap="False" Height="200px" ScrollBars="Vertical" CssClass="style101" />