It is not possible to append data to qvd without loading it, instead you can store into new qvd with datetime stamp in file name. So that next time when you load use wildcard characters for filename. Try this script
Assume Previous QVD Name : Data.qvd
LET FileName= 'Data' & Date(Today(), 'YYYYMMDD') & '.qvd';
STORE Data into $(FielName);
Next time when you are loading this QVDs use this
Hope this helps you.
Except Buffer incremental load in any other incremental process you will need to load the QVD and then create another QVD with the old QVD name. So if you have not tried the Buffer incremental then please take a look from QlikView reference manual or help.
The QVD is automatically maintained in case of buffer incremental.