The one question is, how would you want to check whether a file has been changed (I assume the content), which has been delivered previously?
Other than that you can include the filename by using filebasename() as filename, for each record. Then you read in the existing ones first (from QVD), and read only the records "where not exists(filename,filebasename() ).
For the files which has been changed, you have to include additional function called filetime(), which would look at the creation time of the file. Then you can have a field called filebase()&'_'&filetime() as FileNameTime and when reading in new files you use the condition "where not exists(FileNameTime,filebasename() &'_'&filetime()).
Hi I am not realy sure if i understand what you are up to, but check this if it will help...
Max(Num(date)) as MaxDate
Let MaxDate= peek('MaxDate',0,'Max_Date');
FOR Each File in FileList ('lib://.../*.xlsx');
LET FileDate = num(FileTime('$(file)'));
IF $(FileDate)>$(MaxDate) THEN
This part makes sure it loads only new or changed file. I dont know where does your "date" field come from.
Hopes it help