Help with URL Button to add child record and then save automatically

Thank you for the info. To answer your question, this button would actually be on a report so I'd like it to reload back to that report. This report also displays the last activity created, so the user will be able to verify that the button worked.

EDIT: I defined $URL to the report, but am met with an error page. However, the record did save properly.
ERROR: "This XML file does not appear to have any style information associated with it. The document tree is shown below.