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    // [Template]
    [EventSubscriber(ObjectType::Codeunit, Codeunit::"MOB Item Reference Mgt.", 'OnBeforeSearchItemReference', '', true, true)]
    local procedure OnBeforeSearchItemReference(_ScannedBarcode: Code[50]; var _ReturnItemNo: Code[20]; var _ReturnVariantCode: Code[10]; var _IsHandled: Boolean)
    begin
    end;

Example: 
(note: Searching for GTIN is a standard feature since MOB5.24 an no longer needs a customization in newer versions)

    // [Example]: If Item is found by filtering on GTIN then do not search through Item References
    [EventSubscriber(ObjectType::Codeunit, Codeunit::"MOB Item Reference Mgt.", 'OnBeforeSearchItemReference', '', true, true)]
    local procedure MyOnBeforeSearchItemReference(_ScannedBarcode: Code[50]; var _ReturnItemNo: Code[20]; var _ReturnVariantCode: Code[10]; var _IsHandled: Boolean)
    var
        Item: Record Item;
    begin
        Item.SetRange(GTIN, _ScannedBarcode);
        if Item.FindFirst() then begin
            _ReturnItemNo := Item."No.";
            _IsHandled := true;
        end;
    end;

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