If I understand correctly, you want to load your existing QVD, then concatenate the new data and store the concatenated table back into the QVD:
DATA:
LOAD Dim1,
Sales
FROM QVD.qvd (qvd);
// this table will be autoconcatenated,same fields used like above
LOAD Dim1,
Sales
FROM NewData;
STORE DATA INTO QVD.qvd (qvd);