Sorry, but script triggers does not work with IWP.
And the same goes for automatic updating of calculated fields when a value is changed in one of the fields involved in the calculation.
Only a commit or another action that forces data to be sent to the server will result in an update.
So I am afraid that you will have to have some kind of an update button. It could be as simple as just letting the button do the commit.
If you want your user to keep focus to the field you could choose to attach a small script to the button: Committing and then go to field.
Maybe somebody else has a better advice, but I believe that this is as far as IWP goes, for now. Lets hope that script triggers and a lot of other more advanced features will find their way into IWP in a future version of FileMaker.
... if you where using CWP ... this would of course be possible to solve.
I know it´s not generally supported by filemaker and that there are
limitations but what I am doing is suppoes to work.
See also the Document about Scripttriggers:
1. as I described it it works absolutey beautifully in firefox, safari etc.
only Internet Explorer fails.
2. The problem is not the script trigger itself, but the Dropdown-List. As
soon as the dropdownfield is also defined as a button with the script
(which is necessary to make the sripttrigger work later) you cannot
change the value of the dropdownlist anymore.
So until now I do not even know it the scripttrigger would work because
I cannot change the value.