Insert values on Windows Dialog from Delphi Dialog

Question

I want to know if there's a way to insert, for example, a FilePath in a DialogBox opened by Windows itself, but inserted from a Delphi variable to the Windows Dialog? Something like, click on an Upload button in any website that does open the File Explorer Dialog, and in Delphi send the value of the Path to the File Explorer of Website.

PS : I already have the code to get his HWND handle.

I don't know if this is possible, or is there's a way to do it.

Edit : A Select File from the site, what I want is simply to input the FilePath of this site by an app variable in Delphi.