At the moment we have a problem. The code is like this for example:

opportunity.SalesResultEUR = opportunity.SalesResult / ExchangeRate;

so I'm sure that it was possible to call the BusinessRule through ChangeEvent and immediately see the new Value of the Property in the dedicated control on OpportunityDetails - wich is a custom smartpart btw. The same is happening if we try to do that trough a Codesnipped-Property or a calculated Field.

So you're not looking to do this though a refresh on the server......

and you don't want to simply change the form control directly.....

txtSalesResultEUR.Text =

so you need to do some javascript or AJAX stuff?

You probably need to invoke the refresher service in the UI to force an update in the form.

e.g.

IPanelRefreshService refresher = PageWorkItem.Services.Get<IPanelRefreshService>();

refresher.RefreshAll();