Do you have something to tell you when that field has been updated? e.g. updated flag / date?
If so then you can do an incremental load which is loading the QVD, loading any changes and then re-saving the QVD
Have a read here:
Ok in that case then you should be able to do an incremental load, you will need a key field for this
The logic will depend on your situation of course but I imagine it will go something like:
1- check date updated and load in changed rows from SQL
2- Reload the relevant QVD using a not exists load to only load the rows which haven't changed and concatenante this to the existing data
3- Re-save the data in to the original QVD
The link I provided will hopefully help you work through it.