Hello, i'm trying to do a very simple thing:

suppose I have a custom summary recalculation that takes quite some time to be evaluated.
I would like to bring to the user interface a label with a "please wait" content while the grid is recalculating as  soon as  a groupByAreaMulti element is changed.
I'm trying to intercept WHEN the calculation ends but I didn't find any method on the SummaryCalculator class that I'm implementing that tells me when the whole calculation end.
As far as I'm concerned  I can raise custom events in the overrided EndCalculation method that can be intercepted by the main UI thred,

I can use the xamDataGrid Grouping  or Grouped events to know when the calculation starts:
I can also use the xamdatagrid recordsinViewChanged to find when the grid is ready.
The problem is that  when i'm trying to use a simple dispatcher.invoke inside these methods to set the label content, nothing happens to the UI .

Thanks, Valerio