Access 2013 - Update fields on  form

I have an access 2013 form that pops-up when an acrobat file is saved (by double clicking a field on another form) - the form has both pop-up and modal properties marked yes

In the pop-up form there is a button that when clicked opens the acrobat file and allows the user to resize the acrobat file

I update a text box that recalculates and displays the acrobat file size on the pop-up by double clicking the text box

What I would like to do is after I close the acrobat file have the text box that shows the file size automatically update. I tried using the on got focus event for the pop-up form, but that does not appear to trigger when I close the acrobat file

Is there an event that triggers and I can use to update the file size?

Thanks