make component interactive view wait until all files all uploaded

Hi I am working on making a dashboard that starts by asking the user to upload 4 separate excel files. then data analysis takes place, and a few charts and table summarize the data. my problem is since I am defining a default value for each excel file every time that i open the interactive view it already has all the content filled with default value. how can i make it wait until all 4 files are uploaded before showing any data? I tried using refresh button widget and couldn’t make it work! any suggestion is greatly appreciated!