When you say you don't get any results do you mean that no records are returned or do you mean that your Rolling_Total is blank ?
Your DSUM is based on summing the Rolling_Total column. But if this column has no data (is all zero) in it then summing will still produce zeros. Moreover, you don't mention that Rolling_Total is even included in the "02c-02 Sum individual HAPS" query. Did you really mean to use SumOfEMISSION_LBS in your DSUM?