There is no built-in procedure for that, but you can achieve it this way:
-Create an htm file with the necessary code to close the browser.
-Call this htm page from you POST-FORM trigger.
The code of the htm page could be something like this:
win = top;
win.opener = top;
Then, assuming that you put it in your webutil directory, you can put this code in your POST-FORM trigger: