How can I force an AngluarJS form to realize required fields have been filled?

[ZigZigZig]

I've written an Excel VBA macro to paste some data into an AngularJS form -- it opens an Internet Explorer (11) window, navigates to the page containing the form, and crawls the document tree looking for certain elements by their ID, changing their values from blank to non-blank strings from the Excel sheet. However, when I submit the form, the form logic treats all the required fields as if they were still blank, drawing a red box around the supposed offending fields. (I can intervene at this point by clicking into each field, typing a random character at the end of the pasted data and immediately deleting it, and this triggers the logic that the required field is now filled.)