in my menu program for updating my lookup file and it worked fine at the first synchronization. Then I modified the lookup file on Windows using Excel2CSPro tool. In which folder of Dropbox should I put the new lookup file if I want to update it on my tablet?
You shouldn't manually put the file anywhere on Dropbox. The easiest way for you to update the data is to open your modified file in Data Viewer and then select File -> Synchronize. You can then PUT the cases to Dropbox.